A few suggestions.
- Cultivate a spirit of detachment. Arise every morning and say "it's over". Today is not the day that she is going to realize that she needs you to load the dishwasher so much that she wants a romantic relationship. It's. Not. Gonna. Happen. And that's o.k.
- Take nothing personal. When Michelle Kowkittykat comes meowing and demanding to be brushed, she does not intend to interrupt my work; she has needs, that's all. Likewise, when the drunken ex shows pictures of the beauty of Puget Sound on the cellphone that you are still making payments on, she is merely expressing her joy in nature; she's not really talking about the lawyer with a nice income who took her there and paid for her drinks.
- Get out and talk with someone new every day. There are more than seven billion people on this planet. If only one-one hundredth of one-percent of them are better for you than your housemate is, that is over seventy million people. How many have you met?