Mind over matter is one of the methods. However, there is a physical exercise you can do to lengthen the time before ejaculation. it can be done throuh sex but it is easier when masturbating. Masturbate to the point where you feel your ejacualtion coming, then stop! wait 5-7 minutes and do this again. Repeat this for a third time. Doing this 5 days of week, or daily if desired, will enable you to hold off your ejacualtion. Over time your body adapts to getting to the point of ejacualtion without actually ejaculating too soon afterwards.