There'll be a lot of dated info around here, but in general it depends on the circumstances of how you depart UPT. If you DOR (request your way out) you likely have a better chance of getting the job you want vs if you get washed out. I've known guys who DOR'd, got washed out, and even dudes that got FEB'd later in their careers and departed the flying world. Some became JAGs, missileers, and acquisitions officers. I would not go into UPT focused on what happens if you fail. If you genuinely don't like it, then you can quit and the world won't come to and end. If you try and hedge by quitting before you get washed out...well...don't do that. You won't be in a good position to judge just how well or poorly you're doing.
Hang tough on this topic for a week or two and let those who are currently IPs in the training system chime in. They have busy lives and can't always get to the page immediately, but they will show up.