To love and be loved is the best feelings in the world. But how can you stay in love with someone? In this world where everything seems so fast and temporary how can you say that you are still in love with him/her or your just staying with him/her because you're used be with him/her?
Loving someone and staying with someone because you used to is different story. Some people stay not because of love but because they are use to have them they think they are not complete without the other person. Some are afraid of the process of moving on and finding the right person. Some are afraid of making the wrong decision and choosing to give up. And some is afraid of starting over again. BUT THIS WRONG! Staying with someone without love is the worst decision you can ever have. Because you may lost your self in the process and you can never be truly happy.
That is why you need to evaluate your feelings. What you truly feel is very important. If you think you are losing your feelings towards your partner then you need to be sure first. If the relationship is toxic to both of you, if you're fighting over pety things, if you don't have time for each other, if you're doubting each other and most specially if you are not happy with the relationship then LEAVE. Because is better to leave than to stay in the wrong relationship.