Relationship charity Relate said people often put so much pressure on themselves to have “amazing sex” that they end up avoiding it altogether or do not notice what is actually good about their sex lives.
It has carried out research in collaboration with Marriage Care and Relationships Scotland, which is to be published in full in September.
The YouGov study of around 6,000 UK adults found just 45% said they were “fairly satisfied” or “very satisfied” with their sex life, while 51% said they had not had sex in the past month.
Relate, which provided more than 20,000 sessions of sex therapy in 2013/14, said couples often say they want to bring the spontaneity back, but sex is rarely truly spontaneous and busy people sometimes have to plan for intimacy.
The charity also recommends that couples should not shy away from planning sex or kissing and cuddling in front of their children - in the past, parents were often taught to avoid showing physical affection in front of the kids but it is actually reassuring for them to see their parents love one another.
Psychosexual therapist and Relate Institute lecturer Cate Campbell said: “It’s sad that so few people are sexually satisfied and put pressure on themselves to perform. Noticing what is going well, rather than dwelling on problems, is quite difficult when we’re all bombarded with messages about how sex ‘ought’ to be.
“Sex definitely doesn’t have to be disappointing - there’s plenty that can turn your situation around so you can enjoy a sustained, fulfilling sex life.
“What constitutes a satisfying sex life can vary wildly from one person to the next, so working out what makes you tick is a great starting point. People may feel concerned if they haven’t had sex in the past month but there are plenty of other ways to be sexy that don’t involve full intercourse.”