This is a common mistake and a very common question right here on this humble tumble.
you must push past this cycle and finish what you started and then move onto the next project and then finish what you started and again and again and again.
one of the great lessons of my life is that no piece of artwork is ever finished it’s just done. molding and crafting and getting it just right is a beautiful thing… and for me it’s where the magic happens. but then learn to let go. learn to trust the process.
a nice thing to do is put it away for a while, a couple of days, clear your mind, work on something else and come back to it. sometimes new ideas reveal themselves that bring the whole piece together or you may reread it and find yourself relieved that it doesn’t suck as much as he thought it did