Have you ever been in a situation/relation where you were not a priority but merely an option?
I have read about a 30-year-old girl who has a boyfriend who doesn't want to marry her yet because he needs to spend 6 more years fooling around fulfilling his ambition. He has been good to her since day 1 but didn't promised anything and never discussed about wedding plans ever. Isn't that clear that he is not so into her ready to settle down?
Sometimes it still hurts even if you already knew it right from the start.... So don't make anybody your priority, if you're just his/her option.