It is a little frustrating to me when people are so hard 'party liners' that they make up excuses for the people who are supposed to be representing them. That's backwards. If you feel the person you voted for is doing a good job, then be proud of them for sure, but if they're not, don't.
You should be really upset if the person you voted for is doing stupid stuff, or ignoring what is best for you! You should be the first to say something you should be demanding better.
As a country I think we need to be a little more honest. It's okay to vote for someone, and actually expect that they do a goo job. It's also okay to admit that someone you voted for made a mistake, and still be happy with your choice to vote for him/her.
It's even okay to hate the entire system, not vote at all and expect politicians to do their job. Their job is to represent all of us, we need to start expecting that from them.