"Will everyone make it who tries?"

Depends on what you are trying to make it to. So I'd say yes and no. UPS, no, no promises, but I just flew with a turboprop guy who got hired a year ago. Is a promise required for this to be a worthy career? What promises do doctors, lawyers, cops, or firemen have? I'm not sure the promise Skyhigh seeks can be found anywhere....

A happy career depends a lot on the persons demands. Skyhigh's demands were very high. He wouldn't consider SWA. He wouldn't consider World. He wouldn't consider international flying (all things I'd have considered). In fact, Skyhigh wouldn't consider anything where he can't easily commute (his own words). Odds were stacked against him. Personally, there are many lesser flying jobs I'd have been happy with. Odds become more stacked in my favor the more flexible I am.

One thing for sure. If you quit, you have zero chance.