There will always come a point in your relationship where you would honestly wonder whether you have left something better out there by sticking to your partner. If your lover is a gaslighter, a manipulator, or a psychopath, then, of course, it is more than alright to seek someone better. You don’t need to hold on to your partner at all. But, if you are blessed with a person who is otherwise good in all the aspects and you just try to find someone else because you are either bored or fed up with the person you are with now, then you are on the wrong track.
When you stick with a person for a long time, it is natural that you would feel lethargic and there will not be any new happenings in your lives. You might even come to a state where you can predict the next action of your lover, but be grateful that you are in such a state. You are only too much comfortable with your loved one and if you try to leave him/her to find someone better, you can even end up with someone worse.
If your love is powerful, you would always wake up with the feeling that you are in safe hands and you would feel happy to be with your partner. It is easy to break up and find someone else. But even that affair would come to a lethargic state at one point. Just keep in your mind that there is no one ‘perfect’ out there for you. Everyone is born with unique traits and no matter who that is, you will always have to work on your relationship. Every relationship needs some ‘work’ and for some, that can even be ‘a lot of work’.
So, be happy with the one you have. If your relationship is not going too well, then work on that to make it better. The grass may look fresh on the other side of the fence, but you know well about the side you are staying and if you water it a bit, then even your side would look much better!