1) Any action is greater than no action. It doesn't matter how much you suck at something. Do it. Congrats, you've beaten everyone who never started.
2) Finish things. No matter how ugly it is. Even if you have to half-kill yourself to drag it that last inch over the line. Congrats, you've beaten everyone who never finished.
3) Your worst effort is probably better than average. Stop obsessing about the 1% best. That's not who you're competing against. You're competing against the pool of real people a company / project could afford to hire, who are available to hire.
4) Everyone starts off terrible at everything. No movie covers the 10,000 hours someone is learning: that's why training montages are a cliché.
5) Forgive yourself. It's okay not to be spectacular every minute of every day. Consistency of effort is more valuable than cyclical manic-depression. The key to becoming better starts with accepting and being happy with where you're starting from.