When I was a young and eager mountain bike enthusiast some really long time ago like the mid-80s, there was a trail I wanted to be able to ride up at the West Hartford reservoir property. I spent a lot of time working each pitch of it, keeping at it until I could get cleanly up that pitch and then moving to the next one. Probably took me a few weeks and then I could do the whole thing, every time. Just practice.
However, I really trashed my achilles with all the mounts and starts on the hill. Took a long time to recover.