People have a basic drive to evolve and change. According to the psychologists Arthur Aron and Elaine Aron, this is our need for “self-expansion”. Thus any chance to self-expand should be rewarding, and if you can do it with your romantic partner, then your relationship will benefit. Research confirms that when couples engage in anything that feels new, exciting, interesting and/or challenging, their satisfaction with their relationship increases.
Now in an article in Journal of Personality and Social Psychology Amy Muise at York University and her colleagues have taken things further, laying out evidence that a major part of the reason that participating in self-expanding activities is good for relationships is that it boosts your sexual desire for your partner and increases the likelihood you will have rewarding sex. Apparently this is particularly the case for people in long-term relationships.