You're 18... give it time.
I think "give it time" is good advice if you have a project which is not very successful now but is on the ground running and is growing quickly, but I can't think of anything I'm doing that falls into that category.
A lot of your apparent failures will seem completely meaningless in the future. I would count doing poorly in match/science contests under those, as well as the blog. Are those things really important in the long run?
And some of your other failures will be very important in the years to come. You've already learnt how badly things can blow up if you don't formalise your business arrangements in writing, for example.
It's sounds cliche, but set some concrete goals for where you want to be 5 to 10 years from now and focus on the things that will get you there. Strip out the rest, but keep the things you are passionate about even if they don't have much practical value.