The other person broke up with the singer because they had to. The singer understands but would rather not have broken up. So to stop the other person from feeling bad (because the singer still cares about them) he's going to "keep your memory vague" and not sit and think about that person and make the situation even more difficult for both of them.
He's accepting that it's over and trying not to make the situation harder than it is even though he wishes it wasn't over.
I think this song is about a one sided break up.
The other person broke up with the singer because they had to. The singer understands but would rather not have broken up. So to stop the other person from feeling bad (because the singer still cares about them) he's going to "keep your memory vague" and not sit and think about that person and make the situation even more difficult for both of them.
He's accepting that it's over and trying not to make the situation harder than it is even though he wishes it wasn't over.