I did my first board break recently for my yellow belt test. It made me realize that I need to badly work on my targeting. I was glad I went to practice that morning because I'm friends with one of the black belts there and she offered to help prepare me for my test. That was when I first found out that I would have to break a board. Nobody told me before hand. At least she helped me mentally prepare for the board break. I can't wait to break my next board because I felt very proud of myself after completing the break.
If you're tired, kick some more. Your opponent most likely has extra kicks to spare on you.