Feeling down because of friendship

I feel really sad when I got ignored by those people who I considered as online friends 😕. I don't know, sometimes I feel like these people are good and I can trust. But if they ignored me for days, I start to feel doubtful.. like maybe I should just give up for this friendship, it's just an online friendship after all 😟. I don't get it.. sometimes they said they would help me, be there for me, the other days they'd ignore me like I wasnt there at all.. I have low self esteem and this friendship made me overthink a lot even tho it's just online and I know it won't last. What should I do to let go of this sadness?