Here is a experiment proven fact for you: second guessing is the root of regret, wondering if things could have been done better is what destroys the pursuit of happiness. You cannot allow yourself to procrastinate because of indecisiveness. This is one of the main reasons why people procrastinate, and it is a terrible reason. It makes starting projects more of an ordeal than finishing them. Imagine if you are indecisive your whole life, and you are on your death bed. You will have accomplished little and it would suck! you'd want to go back in time and tell yourself to start SOMETHING, anything. So. next time you catch yourself second guessing, imagine a future you telling yourself to start something, anything. You have absolutely nothing to lose. again, You have absolutely nothing at all to lose. You mess up a page on your sketchbook? screw it, you tried and you can try again and once the pages are filled you can buy another one. Where is the risk really? Just keep going. Seize the day, the moment, the opportunities, whatever it is you want to do, say yes to it and give it a try.