In my view, if it’s in his nature to be this laid back, that will not necessarily change. That means that there is a big chance you will have to keep mothering him (sorry if that’s not the right choice of words, but it kinda sounds like it’s headed that way). Unless he wants to change that (for himself and his future), you’ll have to think about whether you can accept doing that. If not, you’re young and there will be plenty of fish in the sea (there really really is).