How do get used to being alone ?

Basically, the title. I'm someone who's used to doing everything I can for the people who are important for me. I have a small circle of friends and I'm kind of an introvert with a busy schedule, so I only have a few people I can count on.

Lately Ive been feeling like don't get the same effort from my friends or loved ones, that i usually put for them. Rarely does someone in my life reciprocate the effort I put into our friendships.

Sorry for the rant, I just want to know how can I learn to live with this feeling ? Especially on the big days, valentine's day, birthdays etc.