It's hard to do but it does help a tiny bit: You did the best
  you could at the time. You love that girl with all your heart
  and soul as does Linda. You have done all that can be done. But
  you remember 18: You need independence. You need to "break away"
  - it's almost a compulsion that can't be helped. I don't have
  the details - but i remember being there. And i was a jerk to
  everybody I loved.... The more I loved someone, the worse thay
  got treated. one girlfriend I had at college, I treated her
  awfully (I thought i was being "funny" but I was just being
  hurtful). I never forgot how bad/stupid/immature I was, and I
  vowed (after I was about 24-25) to not be that way again. And
  I've worked on it - and keep working on the "dark side" ever
  since. "You only hurt the ones you love" is the truth. You did
  all you can do, John. But feeling guilty is no... "