You’ll lose some years-long friendships to distance. The ones built on real stuff survive the time zones.

Proximity does a lot of the work in a friendship, and when it goes some friendships turn out to have been mostly proximity. That is not betrayal on either side. What survives distance tends to be built on things you actually said to each other rather than on sharing a timetable. Losing some of them is normal and still worth being sad about.

Choose two or three people worth the effort and make the effort specific: a standing call, a message every Sunday, a visit with a date on it. When somebody gets back in touch after months, answer warmly rather than apologising for the gap.