I run and I lift weights. A little more of the latter than the former, but I used to run more than I do of both.
The thing about running, was that there was hardly ever any drama. I got hit by a car once, stung by a hornet that flew into my mouth and, of course, fallen down a bunch of times over the years. The only routine angst I regularly had, was when I was training for marathons. I would have a lot of apprehension at the prospect of going out for 2-3 hours of continuous running.
With weight lifting, there is almost always drama. I've been doing clean and jerk lately and I start at an easy weight and add 5-10 lbs on successive lifts. About once in ten times, I flawlessly work my way up the ladder. The other nine times, I struggle. I will get to a weight below what I know I can do and then I either can't lift it or it is inordinately hard to do and I can't progress higher.
Sometimes I can break through the blockage by just lifting that weight a few times till it gets easy. This works about one time in three. The other times, I will go back to a lower weight, to get "the feel" back and then work up from there. What is this "feel"? Hard to say. Some mixture of effort, timing and technique, which makes a heavy lift feel easy and elegant.
Just to make this easy to explain: The current numbers: Almost every session, I will make 150 lbs. though it's pretty rare to get there easily. I probably make 155 more than half of every work-out, but I really have to have the feel to do it, so it's a break-through lift. Maybe one time in three, I hit 160 lbs.
Yesterday was a perfect example: I struggled to get to 150 and ended up doing a dozen lifts at 150 or 145 before, on the 19th lift, doing 155 so easily that I even "tried" for 160 immediately afterwards.