4. "I need a raise because I'm having personal problems..."
Having a baby? Taking care of a sick relative? Just bought a house and need to make the mortgage payment?
These things are a huge deal and they're justifiably at the forefront of your mind, but they don't factor into whether or not you deserve a bump in pay.
Again, when trying to convince your boss to invest more money in you, you need solid reasons. So if you hang your hat on personal problems that don't even relate to your job at all, you're automatically at a disadvantage. Now instead of focusing on your professional accomplishments, your boss think you're trying to sway him/her with some kind of sob story. Bosses can be sympathetic and I'm sure many of them are aware of your troubles and feel for you, especially if you have a good enough relationship that you've discussed what's happening in the past. But that sympathy does not -- and should not -- translate into a higher salary.