How do I stop feeling anxious about losing the people in my life?

Remember that you are of the nature to grow old, sick, and die.
So is everyone you will ever love or know.
Your relationships are temporary.
You are temporary.
If you worry about losing those you love, you obviously care for them.
The best thing you can do for yourself or for them is to treasure what you have now and to respect that it will end sometime.

the people in your life are not important. Think about it this way. Only your perception matters. if you continue worrying about other people in any way, you will go insane. Focus 100% on yourself as if life is a game and you are trying to win. not only playing a game to get friend requests and join a guild. You want to become lvl 100 so what do you do? go work out. better yourself, succeed. Then people will send you friend requests because you deserve it and they arent as good as you. they will beg for you to accept their friend request and you wont even want it. think like this. If you keep looking towards the future, then the present will never exist. You cannot bring the future to the present because when you get to the future it is now the present and the future is still ahead. One day, you're gonna die in the present and the future you wanted will still be out there. So stop being a pussy and do what you enjoy. succeed