why is friendship so hard?

So like, I've been talking to this one person for like three months. and, yes, I know its pretty naive to think that someone would dedicate their attention to someone whom they've  known for only three months online. But fuck man!

its so frustrating the way they treat me. I'll be telling them something and all of a sudden the go offline for hours on end, without explanation. I know that they don't owe me their attention, but that just sucks.

or in another instance, they'll ghost me for hours, or even days. and then when they notice me getting upset theyll come back and give a half hearted apology. only to do it again later.

I know it's probably really unhealthy to cling onto a person like them. but it's like I can't help it. every time they respond its like fireworks, and every time they don't its like they worst depression.