I have my PPL and will be taking my instrument rating checkride pretty soon.
My advice for the checkride is just relax and fly like you have been trained. The examiner is not looking for you to be perfect, but looking for you to be a safe pilot. Don't be afraid to go around if you feel your landing isn't going to be good. That shows the examiner you have good judgement. Remember to perform clearing turns before every manuever. I believe it's a checkride failure if you do not do them. Lastly, try not to let one minor mistake get to your head. Try to put it behind you and complete the rest of the checkride to the best of your ability. The best feeling is going to be when you taxi in and the examiner says "Congratulations, you are now a Private Pilot!"