Not all friendships are meant to last forever. Just because you're told that college friends are supposed to be for life, that doesn't mean it's always going to be the case. Every friend you meet is a blessing and they were put in your life for a reason. They could be an acquaintance or they could be someone you felt you were inseparable with.
People change; they grow up and they grow apart. Every friend you make teaches you something about others and about yourself. They were meant to show you what to look for in others, what you can and can't live with. They were put in your lives for the memories you've shared and the experiences you've braved together. The duration of your friendship doesn't define its worth and definitely doesn't put on an expiration date. Just because you grew up together and have been friends for eight years, doesn't mean they won't hurt you or that you have to stay friends. And subsequently, just because you've clicked with someone instantly and became friends in a few short months 100% does NOT mean they are any less of a friend or that they can't be your best friend just because you haven't known them for that long. It boils down to who you can feel your most comfortable with, who will be there for you when the going gets tough, and who won't be. They have their ups and downs, but the good should always outweigh the bad and if it doesn't it's OK to end the friendship; it isn't binding.
You should also never have to feel bad about losing someone. Sometimes things just aren't meant to be. If someone strays away from you to do their own thing, the only thing you can do is move on. Sometimes people have to do things for themselves and you can't beat yourself up about it or wonder where you went wrong. Chances are it had nothing to do with you, so don't stay upset about it, move on because they have. It's sometimes hard to balance friendships on top of other things and when the time is right or a balance can be found, you may gain your friend back. It's always better to give someone a second chance and to forgive but never forget. People have a way of working themselves back into your life and it's natural and okay. They may surprise you with how they've changed and the friendship can come back stronger. It's important, however to remember what went wrong the first time and make sure they don't show signs of what broke you apart originally again. Be kind and open but don't be naive.
Losing a friend is difficult and is something most people dread, but look on the bright side of things. Sometimes you may be better off and sometimes they might be, and if you're lucky you both gain something from the experience. Don't take things personally and accept things as they come. If you're meant to be friends with someone, no matter what, you will be. Whether that be now or in the future, the ones who matter will always come back.