You think too much because you do too little.
All your overthinking goes away the second you start taking action.
The dumb guy who takes action will always run laps around the genius overthinker. The downfall of high-IQ men is overanalyzing everything instead of simply taking things for what they are.
Just take the next step.
You have to summon your inner courage and confidence about yourself. It’s hard to do if you’ve had a string of recent failures, you will have to go deeper inside yourself than you ever have before. It’s possible.
At some point, usually in your 20s, you'll notice that the people around you stop believing in themselves. And no matter how hard you try, you can't save them. By all means, do not let it infect your mind. Stay on your path.