Sex does not equate happiness in a relationship, but it’s pretty damn important. Bad sex can ruin relationships because it can lead to cheating and, of course, lying. That is when sex can become a massive issue and ruin each partner’s happiness.
Let’s not forget sex is intimacy, a different level of closeness that should be appreciated by both parties. Sex should be a pleasurable experience giving you both a break from the stress of your everyday life. Sex is a high, a natural high so you should enjoy every minute of it.
Bad sex could lead to no sex which could lead to a platonic relationship which IS NOT a romantic relationship. For those that choose not to or are unable to be physical for whatever reason such as a disability or religion then that’s an entirely different subject. However once sex is introduced it is an important factor to any relationship. Sex is supposed to be a bonding experience such as holding hands, kissing, hugging, cuddling, etc.
You have to understand sex is more important to some people than others and you won’t always realize that until you are well into your relationship. Some people want sex every day, every other day or once a week whereas your partner may require sex less frequently and even these differences can cause problems.
The key is always compromise and communication. Sex does not make a happy relationship but you’re kidding yourself if you don’t think it’s an important part.