wow...that's a lot of miles, I don't think I would have tackled that for my first...or even now!
I've been using my bike for commuting for years. But it's been mostly as a to and from bus or train. Less 1 - 2 miles each leg. But this summer is what I'd consider my first commute, since it was 6 miles and I wore cycling clothes instead of work clothes, and took a shower at work. I've always been a weekend warrior mountain biker, but this forum made me want to commute. I remember the ride was great, exhilarating, energizing and I felt like He-Man all day long. I hung my bike shorts and shirt in the office like a trophy for all flabby coworkers to see. I drank from my bike water bottle all day long, took it with me to meetings and everywhere, like a badge that says "I'm a badass, I work harder than you at work AND I got here under my own power".
The third day that I did that, I took a long way home 12 miles and included hills. It was a road I've never taken, neither in bus, nor car, nor walking nor by bike. I only knew I could get home that way because mapquest told me so. I was inspired by a coworker that said "Woa, that's a big hill. You should drive it first to check it out", so I rode it that day and it was great. It went up, and I went up, passed a lake. Then I deviated from my planned route to ride a bike path that I didn't know was there. It lead to another lake. Great scenery, great sense of accomplishment.
The reality of it is that my commute is short, and that hill I was proud of conquoring wasn't that big. But the feeling of accomplishment and triumph that I felt wasn't due to miles, or elevation grade or other measurables. It was from succeeding when I didn't know what to expect. I didn't know what I was doing. I didn't know if 6 miles was a lot or a little. I didn't know if my coworker was right when he said it was a big hill. I didn't know if I'd be able to make it to work, or worse, make it home. I didn't know any of those things. But I gave it my best and it was great. I commuted 5 days that week, I don't know what I actually accomplished that week at work but I'll always remember what I accomplished immediatly before and after each day.
Oh, the first day I forgot to bring underwear so I was commando style all day long.