Eg 1. We live in a different country to some family members, so cards and presents have been sent as a regular thing. Since the start, I'd email to let them know when something arrived and say thanks, then a proper thanks again later when it was opened. In contrast, unless we asked, we wouldn't hear anything until months after the birthday (or whatever) when a written thank you card would arrive. All fine, if that's how they do it. However, if they don't hear something has arrived with us, sometimes even before it's had chance to get here, there are questioning emails. I started doing the same as them a little while back, ie not notifying on arrival, and it has caused a lot of bad feeling from them!
Eg 2. A close family member, late for things 9 times out of 10. No good reason, just doing one last chore before setting out, or not watching the time or whatever. I used to be on time for everything and consequently left waiting by myself, so started being a bit later too. Hasn't gone down well.
Eg 3. Friend who always promises things but never delivers. I no longer see why I should either. Again, some bad feeling developed.
Why is it OK for some ppl to be flakey, yet make you feel bad when you do the same? I don't think it's unreasonable to put the same amount of effort into a relationship that the other ppl put in. Although it took me a while to realise this. AIBU?