I think elena choosing stefan was like a sacrifice for elena ,she felt as though she was indebted to him for saving her life ,and so she chose him,this actually proves that she loves damon more ,because she knew if she was to be with damon ,she would always feel guilty that she didnt choose stefan because he saved her life and all,which is why she "had to let him go" ,elena didnt choose love ,she chose "responsibility",meaning the responsibility which she thinks she has ,in other words "stefan".

I think my theory will be backed up in season 4 ,eg,because in the finale , stefan did not save elena,so in season 4 i believe that elena will not feel as though she has that "responsibility" for stefan...and whoever says that elena does not have the exact same feeelings for stefan ,because she is a "vampire" who has the ablity to "shut of all human emotion" and "thats why she does not feel for stefan as much as before" needs to shutup and smell the blloood (LOOOL) ...and stop making excuses

Guys you are probabli gonna want to smack me for saying this but ,i feel as though when elena really really really wants to be with damon ,damon will kinda be like no ,and i think it will be because of stefan and guilt ect ect ...i dont know why...other reason why i think something like this is likely to happen is because the vamp diaries ...take ages to give us delena fans what we want ...anyway its just a opinioun x