How does one survive long periods of ...inaction?

Obviously this doesn't apply to those who are "saving themselves." But, for example, say one spends many of their young adult years in a relationship, then it ends. And they don't have another one for a very very long time, like more than 5 years. How does one survive the lack of sex and or affection and not go crazy? Just wondering. I was thinking of a friend of mine - no one that uses this site.