I used to be like this too. My girlfriend once told me, "Your friends don't take you seriously and nobody expects you to follow through because you don't."
I decided I didn't want to be that guy. So I started following through.
It's the boring part that gets us to quit. You have to pick like 1 or 2 things and eliminate everything else. Make sure the thing you keep is what you desire most to finish, even if you don't feel like doing the work to finish it β focus on why you started and what the end looks like.