Find exercise you enjoy and look forward to. Make it a social thing and get your mates to come along. There's nothing worse than forcing yourself to do something you're not gonna like on a regular basis.
It's not a problem for me, I actually feel worse if I can't work out for whatever reason. I leave the gym on such a high (even if it's been leg day!) and I love the feeling of pushing myself to the limit.
I've been restricted recently because of an ankle sprain and i'm at my wits end!
As someone who has medical problems which have eventually led to diabetes I would suggest taking a gander at your GPs waiting room when there's a diabetes clinic on. That will give you all the motivation you need.