Being in a relationship with someone you love is a great feeling that everyone should experience. However, when you are in a relationship and you doubt the reasons why the other person is dating "someone like you" then sooner or later you start running into problems because of your insecurities.
Being insecure in a relationship is a bad thing, but showing these insecurities to your partner is even worse. This is because people don't really like to be with someone who doesn't respect themselves. The foundation to a healthy relationship is having respect for your partner but also for yourself. But if you can't manage the latter, your partner will also start to doubt the reason why they even like you in the first place.
But what's even worse than not respecting yourself, is when you make your partner the sole reason for your happiness because of your own insecurities. If you can't find happiness outside of your relationship and constantly rely only on her/him, you will start to depend on this person. This means, that if he or she isn't around, you can't be happy. This is a terrible mindset to have and you should do everything to fix it.
Because of this, you should start looking for happiness outside of your relationship. Find something besides your partner that brings happiness into your life and devote your attention to it. You also have to start working on your self-esteem. This way you know your own worth and don't depend on another person to define it for you. You need to make a shift in your mindset or you will just ruin your relationship because you rely too much on the other person.
Whenever you start a relationship with another person, never doubt yourself why the other person chose you. They chose you for a reason and if you don't know it yet, make it your mission to find out. Only this way will you stay in a happy and long lasting relationship.