I agree with divinerguy.
To add to what he said, try to avoid reading the cards when in a high emotional state. Fears can not only affect a reading, but strong hopes can as well. I recently read for a friend who was really hoping for something. The cards seemed to suggest that he would get what he desired, but it didn't actually end up happening.
If I'm doing a reading for myself I make sure I am very calm, and try not to think too hard about the question when I'm shuffling/drawing cards. If I am having trouble being objective with my reading, I pretend that I'm reading for someone else.
Also, I do agree with divinerguy about not reading for yourself too often. I generally only read for myself maybe once a month, unless something comes up which I really want to do a reading on. If you find yourself doing too many self readings, it's easy to get caught up in the subjectivity.
One more point, doing too many readings on the same subject/question is not really a great idea either. This can lead to your hopes/fears showing through in the spread; besides that, it will probably leave you feeling even more confused than before you did a reading.
Anyway, I hope this helps.
Lilli