Ouch This Is Gonna Hurt!
Imagine the following scenario: You rub the palm of your hand with sandpaper until it bleeds (you’re gonna have to go with this for a bit so read on…!). Once the bleeding stops it dries, possibly forms a scab and then after a few days that scab comes off. The most important thing here is not “why am I doing this?!” but that even though your hand is very sore and delicate for the first few days the skin toughens up and is in fact stronger than it was at the end of the process. This is an example of a stress-adaptation curve.
If we were techies we’d draw this curve for you but we’re not we’re cyclists so basically it’s this:
This is exactly what happens when you train; put a strain on the body that it’s not used to (ride harder, faster, longer), rest and recover then next time you’ll be that little bit more prepared (fitter) and you’ll find it easy.
That said you’ll probably go out again and ride to the level of your new fitness so you might struggle still but that’s progress:
“It never gets easier, you just get fitter!”