It's the expectation from society as a whole that gives you some sort of pressure that you are missing out. It's a facade, the happy relationships that you see it's what they sell to believe that they are happy. It's what they also sell on TV, movies and magazine in order to make you think that it makes you complete. It's just a temporarily feeling of happiness due to neurotransmitters in your brain, which changes over time. If you have sex with an escort dopemine is released which gives you a good feeling. But in the end all happiness comes from inside, not from external factors. That's why should focus on goals and work hard to get there, it makes you a stronger person in the long run. A woman will not make you happy, she can only be an addition to that, unless she is a parasite feeding of your greatest asset: Time.