Starting over from the beginning is rarely worth it. Even if you look back at old work and see loads of potential improvement in it, it's almost always a more valuable use of time to push forward and make new work rather than retreading ground. Especially in something as time consuming as animation.
The more you improve, the more fun it will be to look back at old stuff and groan and laugh and watch it get better as you marathon it all and remember what it was like to make it. push ahead!