Everybody have some people in their life and it doesn't matter what relation we've with them. We cherish and love them the most and we want them to stay in our life or stay by our side forever but when they're not willing to stay? They're not willing to cherish you like you do them, then?
At this type of situations you always try your best to convince them to stay but if the other person doesn't want, then? They doesn't care about your emotions, then?
You need to understand that you should try your best but if someone doesn't want to stay so you shouldn't convince them because you can't convince anybody like this because human relation is a bilateral consideration.
If you tried your best but still the other person didn't give you any response it means they didn't care about you or your emotions so simply Let them walk away!
Let them walk away because holding on something which isn't belong to you anymore only make you hurt and restless. You know what, most people are wasting their time and energy to convince people to stay. The energy and time you wasted on them you should applied on yourself because you matter!