I guess in this connected world, everyone expects and maybe even craves instant replies or results. The bad part of this is that when there's this expectation of the other person replying at once, not replying makes some people ASSUME the worst (he/she doesn't like me). Which tends to be a self-fulfilling prophecy because they become a nuisance to you.
Totally get that!! It's out of insecurity and it usually means you like the person wayyyy more than you should initially.
There is a difference between "I just wanted you to know I was thinking about you" and "I've thought about you 12 times in the last 12 minutes and I wanted you to know every single time"?
Just think, if you send communication and the person doesn't respond, assume they didn't see the message so if you send another one, when they do look at their phones/emails there'll be 2 and if you send another one, there'll be 3, etc. Assume if they haven't responded, they haven't seen it so whatever you send will be seen as a block. Look at it that way.
One time I had 6 missed calls and voicemails the night I left my cellphone at work. It was scary when I got it back. It went from casual to concerned to urgent to panic to pissed off. LOL that's some scary shite right there.