Ok started out last April riding a bike have a 21 speed 1973 schwinn varsity.
Any way when I first started out on April i st struggled a LOT But as time went on I got stronger every day.
So far have gone 998 miles since April. Today I get on my bike and went 7 miles and I was struggling bad out of breath legs tried like I never rode a bike Its not hot is a nice cool day .I don't get it I am 64 years old has any one had this happen to you

When did you last ride before today? How long is your normal ride? It is normal to feel stronger on some days than others.

Yes, this happens. Some days just don't feel right. In most cases, it's just a bad day with some other explanation (overtraining with not enough rest, a cold coming on, something else, or just a bad day). Generelly, you try not to be bothered by it and ride again another day.

But you didn't give enough detail for us to guess what's going on. How many days/week do you ride? You say, "every day". Does that mean you don't take days off? Rest is an important component of training.

Asthma

yes, have the same thing, on those days just pedal slowly and see if you improve

I try to ride twice a day with a total of 6/10 miles every day of the week

Last time I went out was yesterday and felt good I did only got 6 hours sleep last night maybe that the problem glad it just not me and others have this problem
Iwill
try again later after dinner and go for a short ride then get 8 hours sleep and see how it goes tomorrow
Thanks Norm

No No No! Take days off! Your body needs rest to accrue the gains that you are getting from cycling. Don't ride more than 5 days a week.

Also, google "overtraining"

There is the possibility you may be coming down with a touch of flu. If so, your heart rate will be elevated somewhat. It is useful to know what your heart rate is on waking and then later in the day.

Check your brakes?

When I first started riding someone told me, "...some days you will have it, and some day's you won't." On the days "I don't" I just pedal slower and enjoy the scenery...

I doubt that you are over training by riding twice a day with an average of 6/10 miles per day. I agree that you might be coming down with something.

No time for sleep. Sign up for the 9k Strava climbing challenge and get riding.

Lack of sleep and even what you have for dinner the night before can impact your energy level.

Overtraining.

Excercise tears down your body. Your body compensates by getting stronger during recovery.

Take an easy week, recover, and you will probably come back stronger.

These are basic training principals. You need to take an easy week once in a while.

Ok I will give it rest for a few days

Everything folks suggested above. And then some.

After hitting my one year anniversary last since resuming cycling after 30 years away, I've become a bit impatient about progress. But at 58 with asthma and a wonky thyroid, I have to be realistic. I can't ride every day at even a moderate level and expect to recover enough to see any progress. And I often don't sleep enough, usually only 3-4 hours a day. That can't be good. But some days I don't have any choice.

Hardest part for me now is to force myself to take it easy on my "recovery" days. Yesterday I *thought* I was taking an easy but longer ride at a very moderate pace. But I wasn't. I kept pushing myself. It was only after my rear wheel was warped by a minor bit of bad road (no fall or injury) and I was forced to ride very slowly and carefully to the LBS, that I realized even when I think I'm taking it easy, I'm not. In order to be sure I didn't damage the wheel any more, I stayed in the smallest chain ring and only the largest (easiest) four rear sprockets. It was such a relaxed, non-stressful and actually somewhat enjoyable 12 mile trip that I realized how much I push myself most days, beyond my comfort zone.

So for now I'm planning only one fairly hard and physically stressful ride a week, and ride only moderately or easily the other 2-4 days. And to enforce it I'll need to stick to the smaller chain ring and easier gears to be sure I'm pedaling steadily but not keeping my body stressed without adequate recovery time.

One of the problems is there are a lot of hills around here
And I do use the gears that's why I modified my ten speed to a
21 speed varisty I was pushing my self with the big chain ring
And have been going along about 15 mph
Today just could not do it but going out on a bit for a 2 mile run
Taking it slow and use the easyer gears
And tonight going to bed by 9 to get 9 hours of sleep
And see how it goes tomorrow

The main thing is before I went to the bike I was s little over weight,
Could hardly walk because of problem with my right leg, was told need knee replacement .
Pre diebetes and some heart problem .
Snice Apirl lost 25 lbs ,leg has gotten a lot better as I can walk now.
Took me off one of my blood pressure meds. Cholesteryl drugs don't need.
Passed stress test with flying colors and was told my heart is fine.
So that old schwinn has done s LOT for me. yea I have been pushing it a bit
But even with what happen this morining I am still a 100%
Better that I was a year ago. And when the weather gets bad I a trainer to bolt on the
Bike and just keep pedaling away

Yes. Same thing happened to me this morning. I alternate 21 mile rides with 12 mile rides, 6 days a week. This morning I was out for my 12 mile and hated life for the first 5 miles, winded and nothing in my legs, I thought WTH. But after mile 5 it seemed to go away and I actual climbed the last hill with some punch.

Nothing wrong with off/need recovery days. Don't fight it it.

OK. in addition to taking off a day or two a week, mix up your riding, don't push the big ring on every ride. Try running on the lower gears one or two rides a week and spin your feet faster. Sounds like you're making a lot of progress, and as you progress you need to change things up a bit to adapt.

This last weekend I rode a lot on Fri, Sat and Sunday and climbed a lot of hills. So even though Monday was a holiday, I did not ride. On Tuesday I did a flat 22 mile ride. Today I didn't ride but went for a walk carrying hand weights and doing some upper body exercise while walking for about 30 minutes.

just got back from a 8 mile ride. Stayed out of the big ring and used the lower gears more. took it easy. It did go a lot better then yesterday

This. Also flats.

My rides range from 20 to 60 miles usually. I find if I ride 3 days in a row it takes a toll, so I don't do that. Also, when my average MPH drops a bunch it can mean I'm getting sick.

I'm sorry, but even if the OP is moving at 105% all the time, he simply cannot "overtrain" riding 12-20 miles per day (in two sessions no less.) Some days the energy level isn't there. It happens. Overtraining is a real thing, people, and it's not just a "Oh, I didn't feel as fast today." It's a diagnosable condition, and you don't want it. It's getting kinda tiring seeing it thrown around so often by the 60-miles-a-week crowd.

I ride every day, averaging over 35 miles per day. That's about 260 miles a week. Yesterday was I think Day #44 without an off day, and my energy level was down a little-- so I only did 74 miles @ 18.4mph. The first hour my legs felt like molasses. Never once did I suspect the fearsome overtraining. I was just tired. I was stronger in the last hour than I had been in the first.

Keep at it, OP. At your miles per week, fitness/health permitting, you could ride seven days a week forever.

A bad day on a bike sure beats a great day at the office .