I've had quite a few therapy clients learn to reach orgasm with a partner if they practice self-stimulation slowly and with much less pressure than usual. You can do this any time, whether you're with a partner or not. Of course, avoid self-stimulation just before you're likely to be sexual with another person. At the root of this approach to sex is the belief that there is a formula for how sex is supposed to go. This belief is one of the main reasons that people get into sexual difficulties.
Formulas are essential to create chemical reactions, but they nearly always stymie sexual reactions.
Working to follow a formula requires people to ignore both their own physical sensations and the signs of their partner's pleasure. It obstructs spontaneity and dictates a script that denies people's uniqueness. Some men get into the habit of thinking about how difficult it's been in the past to reach orgasm when they're having sex with a partner. This slows down arousal and makes orgasm more elusive. Focus on things that are sexy to you.