It's not true that we didn't foresee something specific at the very beginning.  We sometime just tend to make the choice which brings about less pain at that moment.  I did foresee something, but I was willig to take the trouble and the pain to make the decision which might make the next few years of mine miserable.  However miserable would it be, I didn't mind, because I was miserable enough before the decision moment to be desperate about everything, when suddenly hope came,  though immediately followed by frustration.

     Life is a box of chocolate. You'll never know what you are gonna get.  However, it's up to you whether to take the next chocolate or not.  If you don't take it, you even don't get a chance to know how it tastes, bitter or sweet.  Even if it's bitter, I'll take it as long as I am sure I love it, because I know it'll be sweet inside.