Ahem.
Residency can be
cry
a marriage killer... been there, done that.
One of the most important things to note is that if your relationship has any 'flaws', residency will make them more dominant over the good parts of your relationship. Get your daily issues delt with quicky, identify what bothers you and get it out in the open so those issues don't fester in your thoughts. DON'T NAG!!!
Don't whine or cry to your mother/sister/brother/friend about your problems behind your SO's back - this is a No-No! With your SO: talk, argue, solve, move on...
Never, never, ever, say this: "What about my needs?"
Don't confuse personal debt with professional debt. Live within your means, only borrow money for emergencies.
Network with others who have SO's in residency. You don't need to make friends of everybody, just have a few people to talk to about it all
so you don't feel isolated.
Find something to do that contributes to your relationship, do not just sit around the house, this can be brutal. Get a job, work on personal skills, get yourself back in school, etc. If you have children, get them out of the house as well. Network with parents with similarly aged kids as your own, share parental duties.
GET SEVERAL BABYSITTERS THAT YOU CAN TRUST - USE THEM.
Stop watching
Oprah, seriously. Turn off the tv. Stay in shape. Exercise, learn to jog, play tennis, sweat out those harsh days.
Have rip-roaring sex with your SO, whenever possible.