My girlfriend and I argue all the time because she thinks I am still in love with my ex-girlfriend. What should I do to change her mind? We have been together for almost a year but whenever we fight, this comes up and I can’t seem to change her mind. When we are not fighting, everything is great between us, but I feel as if she can’t get over some aspect of my past and that gets in the way of us evolving and moving towards something stronger. I want to build trust but can’t because she won’t even consider what I have to say when she’s angry. Should I assume there is no way of fixing this?
If something isn’t resolved, it will keep coming back. If she isn’t willing to accept what you have to say, check how you’re saying it. Talk about this when you aren’t fighting and try being more empathetic so you can see where she’s coming from. Try and find out why she feels this way and ask her what you can do to make her see things from your perspective. Talk about whether you’re still in contact with your ex, for instance, and if this bothers her in some way. This is more of a communication issue than one of trust because being better at one will lead to the other. Learn to talk about difficult subjects all the time, not just during an argument, because that is the way to get closer to each other and get better at resolving issues that cause friction.

How should I deal with a roommate who always tries to steal attention from guys who are talking to me? She’s a friend so I don’t want to be rude.
Setting boundaries isn’t being rude; it’s standing up for yourself and explaining as clearly as possible that some things are okay and some things aren’t. Confrontation isn’t easy but it is necessary when someone doesn’t understand why their actions are causing you pain in some way.