As someone who has had trouble falling in with friends or work or hobbies, I have noticed two things that helped:
1) Acquaintances.
Enthusiasm is infectious.
If people you know are infected with enthusiasm, all you have to do in order to get enthusiastic is hang around them and commit to seriously trying what they're enthusiastic about.
2) Say yes.
I hate saying yes.
Nonetheless, the skill of purposefully, deliberately telling myself "no excuses - I will do X at time Y for period Z" helps commit to X and set specific boundaries for an experiment.
At the end of the experiment, I can decide whether I want to continue trying to X.
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Each of those two alone is not enough to try new things.
If you have acquaintances but let yourself wimp out of what they want to do together, you won't leave your comfort zone.
If you commit to trying new stuff but don't have suggestions from other people, you won't leave your comfort zone.
So only combining the two works for me.
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For new skills, hobbies or interests, another factor plays a role:
3) Weeding out fear of failure.
Failure is not your personal failing, it's a product of chance.
If you fail, that doesn't mean you are intrinsically bad at something. It means you are unskilled. Or, often, merely that you were unlucky.
We just don't see it that way because our thinking is too biased and noisy to think in a strict statistical manner.
The confirmation bias alone makes us forget dozens or hundreds of failures each of us went through when we were learning to walk, cook or ride a bike.
We only remember failures that have been particularly spectacular. That makes us feel that all failures are embarassing.
We also focus on the way it's easy NOT to fail at things we already know how to do. That makes us feel that failures are not normal.
So, keep that in mind.
Failing more often than 30% of the time is normal: it means the task is sufficiently challenging.
If you fail more often than 80% of the time, it means you could reconsider your learning approach. Maybe break down a complex task into simpler elements and rehearse those one by one.
Succeeding more often than 60% of the time is the red flag that should get you really worried about your approach to learning. Unless you are specifically rehearsing a task you already know how to do in order to build up your muscle memory, a high success rate means you're just doing the easy thing over and over instead of actually learning.