To be honest, it is really difficult to translate. But I'll try to do my best. Here it is:
May the one who is right continue to be right
Let him/her continue to think (in her/his head)
I can't regret for him/her
Aklı kalmak means "not to stop thinking about something we like".
For example,
-Dün o dükkanda gördüğüm o çantada aklım kaldı. => I can't stop thinking about the bag I saw yesterday in that store. ( because I really loved and I want to buy it)
Here, the case is a bit different. The person who we are talking about probably loves a girl and he can't stop thinking of her. This is what "aklı kalmak" means.
I know my bridge sounds a bit weird, I hope I could explain the meaning.