Yesterday I rode my bike for only the second time this year (it was warm enough, not raining). I rode for an hour - about 12 miles, not all that far -- and when I got done it wasn't my legs (they were fine) or my wind (not a problem) and I was exhilirated, not exhausted.
No, what gave out was my seat bones, which aren't used to the bike seat any more, and they were letting me know they'd had enough