Cole: You don't need to envy me, Solas. You can find happiness in your own way.
Solas: I apologize for disturbing you, Cole. I am not a spirit, and sometimes it is hard to remember such simple truths.
Cole: They are not gone so long as you remember them.
Solas: I know.
Cole: But you could let them go.
Solas: I know that as well.
Cole: You didn't do it to be right. You did it to save them.
Inquisitor: Solas, what is Cole talking about?
Solas: A mistake. One of many made by a much younger elf who was certain he knew everything.
Cole: You weren't wrong, though.
Solas: Thank you, Cole.
Sounds a lot like what he does to Lavellan in the end, too! As if he just repeated his mistake, in a different way (since the way Cole talks is really vague), but still...very interesting.
Finding happiness in his own way - Lavellan as a romantic interest
They are not gone so long as you remember them - A part of our elf is always with him
You could let them go - Well...we know that he pretty much left Lavellan, thus letting go of her
You didn't do it to be right, but to save them - I guess he wanted to save our Inquisitor, in a way, from himself
A mistake made by an elf who thought he knew everything - He still thinks he knows what is best and right for Lavellan, without taking her own opinion into consideration
I know that you can't really make a parallel between the two things, but I guess you can compare it to the mistakes he made while falling for our Inquisitor. I just like to compare such things, because it's so interesting to see that Solas can never be free from terrible mistakes. Poor guy.