If you don't have any hills, I suggest you go out for your regular ride, whether is 20 or 30 miles. When you get home and you are tired and worn out.... go out and do it again striving for a faster speed. When you do long hill climbs, you have to push yourself beyond what you ever believed you could accomplish. There are times, when you don't lookup the mountain and you measure your progress by the weeds that are five feet ahead. When your leggs ache and just want to quit, you usually have at least 5 miles to go. If a day is windy, go train in it, if you ride at 14 mph, push to ride in the wind at 13-14 not 12 where you are comfortable.