I'm also aware before I start something, that if things don't go to plan, a do over could well be on the cards.
For example, I painted the backscene for Bodmin Moor three times. Each time I thought it was fine when finished, but after a few days I scrapped it and started again using a different reference image. It's quite hard to be objective when you're too close to the work and just standing back is not really good enough. This has been the case many times and I don't feel gutted that I have to start again, I actually find it rather refreshing and the work improves immensely too.