When you are having a bad time try to recite Tara mantra and concentrate on a very bright and warm white light in your heart giving joy and pleasant feelings to every part of your body. Slowly let this light come out of your body and give the same to other beings too. Do this for a few minutes and relax for few minutes alternately. See how you feel with this.
Also by Ringu Rinpoche. Thanks to Areerat for the forwarded text.
Tara Mantra: Om Tare Tuttare Ture Soha