Actually I made two.

I thought when I helped someone that when the time came they would help me if I needed help.
That was my first mistake.

My second mistake?
Thinking that if someone I had helped didn't help me back then the assistance I had given was not valued by them and that I had been no help at all.
When in fact, more likely, I had helped them enough that they were now doing their thing and too busy to look back as they are now helping others.

Actuallu I made no mistake at all.

You shouldn't need to follow up that email you sent.
You shouldn't need to remind people of that meeting you booked.
You shouldn't need to let hem know again that you are there for them.

BUT

You shouldn't need to be reminded that not everyone is perfect
You shouldn't need to be reminded that sometimes people don't understand
You shouldn't need to be reminded that sometimes people forget

You shouldn't need to be reminded that sometimes people are waiting to see that you care, that you understand, that you are not like all those other people who keep telling them they shouldn't.