How do you know when a connection has fizzled out?

Before I go on, I want to clarify that I'm not talking about anyone I've spoken to on this forum. I don't want anyone to get spooked!

I have be-friended (or attempted to) people in the past, and we'd go through a wave of speaking fairly regularly, before things fizzle out and we're speaking a lot less frequently if at all. If it's a mutual sense of "we don't have anything to say to each other" then that's fine, but I have found myself on both sides of the coin where there's an awkwardness of how to deal with it.

There's people who I'd hear from a lot less regularly. They'd read messages but not reply, and back then I would still bombard them with messages without considering it's probably actually putting them off. In many cases, that's what gets me blocked. More recently, I tried to rationalise it (they're probably busy or have limited energy). I did ask someone about it ("are we cool?") and they were honest with me and said that they didn't feel the friendship was working for them. I'm glad they told me but I felt guilty that they didn't feel they could without me asking first.

I think that put my guard up a bit. I already had a sense of "do they not like me anymore?" if someone disappeared, but it's a bit more intensified. While there are some friendships which naturally fizzled out as it was apparent we didn't have much in common, there's others where I didn't really understand why it happened, because in some cases me and the other person considered each other 'best friends' but suddenly we weren't talking and I didn't understand why. They may not have felt that same way anymore (which is completely fine) but I'm not good at taking a hint. Mainly cos I can't pick up on them, and it's uncomfortable for both parties to confront it head-on.

Someone may just have things going on in their life, and I wouldn't want to make a knee-jerk decision. As a result I probably do hang on for as long as I can (to the point I've exhausted myself) until it's clear that it's no longer reciprocal.

I'm never angry with the other person in this instance. Perhaps saddened but I try and empathise with them over the fact they've probably got things going on and it's not something they would want at this moment in time. It is difficult without knowing exactly though, and it's hard when you would want a clear answer and you realise that it's probably not going to arrive.

On the flip side, there's other situations where I realise that the friendship isn't what I want either, and I'm not exactly one to be brave enough to say anything because I don't want to hurt them, even though I'd welcome them saying it to me (were that the case). As a result I tend to let it drift.

I could have handled all of it a bit better, but I wondered how others handled it. I hope this makes some sense.