You have had responses all over the map. May I suggest you decide on what the worst thing that could happen will be? From your description it looks to be not being able to finish. You've said that is doable, just not desirable. If, in fact, that is the case why not do it? If you go all the way you have not only met a challenge, you've had fun; a real emotional high. If you don't finish, so what? The only failures in life are those who don't dare.