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It’s fair to say that most climbers would improve if they followed three rules:

Try harder. 

Find the best climber near you or someone who is progressing quickly. Watch them when they try something near their limit.  That is the level of effort you want to have when you climb.

Stay Healthy

End your climbing session before you get exhausted. Drink water. If a move hurts, stop trying it.  Develop well-rounded hand strength rather than relying on only one or two grip positions.  Do some opposition work.

This doesn't have to take up a lot of time.  A little work done consistently goes a long way.  You're just looking for the minimum effective dose.

When you’re not trying harder, move better.

We can’t physically try hard every minute of every session.  Ideally, we should all be warming up and cooling down at some point.  When you aren’t trying to rip holds off the wall, put all of your focus into how you move.
If you only know how to climb using momentum, climb slowly.  It requires more tension to move slowly, and gives you more time to feel how you move through space.  If you want to be able to do bigger moves, practice driving through your legs and your pulling arm during every move.  You want to be comfortable using higher feet?  Climb some of your warmups by only hand-foot matching.

Kurt Vonnegut said, “We are what we pretend to be.”  Pretend to be a good climber.