Over the years you have so many friendships, some last years, some last months, some only last a semester.
Friendships are a complex thing, always changing, always growing. But sometimes, things stop growing in a positive way, but more often in a negative way. You start to grow apart, you talk less, stop really hanging out, seeing each other gets kind of awkward. But this is totally normal, people grow apart. Your life is changing and so is theirs, and your lives might not be going in the same direction. If you don't really talk that often and you don't miss talking to them, then keeping the friendship isn't worth it.
Life is too short to dwell on friendships that aren't making you happy or bringing light into your life.
Life is complicated, to say the least, so having a friendship that feels like a chore isn't helping you live your best life. Dropping this friend doesn't mean you don't care about them or don't want them to succeed or anything like that. You will always care about that person, you just need to be able to grow and not have a friendship that makes you feel less or makes you feel any sort of negative emotion.
Who knows, in a couple of years your paths could cross and being friends just clicks and makes sense again.
Never feel guilty for bettering yourself, if you feel like ending the friendship or putting it on the back burner is going to help you, then don't hesitate to do it. You should be your top priority not someone else. Trust me, it's so difficult to do this, especially if you have mutual friends with this person, but it will get easier with time.