That's sad to hear and I hope you manage the guilt you feel and find some kindness for yourself from time to time.

Regret makes a terrible companion, I have them too, but I try to remember that I made decisions based on what I knew at the time and that looking back on them now means I see them differently and with fresh (more wise or knowledgeable) eyes and mind. Not a consolation comment for you, just an observation. But, be kind on yourself a little bit too...and (like I think you have) carry the lesson forward.

Thanks for sharing, I appreciate it. I wanted to share some of the situation here in this post but decided against it out if respect for my friend,but there's still a lesson in the post for those who choose to see it right?