I think that, as with every U2 song, it feels like Bono has a personal message for everyone listening to the song ;-)
But I think the general message of UC is indeed the "release, restart, reboot. You're free to go".
In the book that comes with the deluxe edition Bono says that he wrote the song with a character in mind, which is the same character as the one in Moment ofSurrender. It's a soldier who came back from a mission traumatised and completely lost control over his life, but also took his wife down with him. UCstart at the point where he has hit rock bottom and just at the moment