I think I just identified the first big mistake I made in life.
When I was in 4th grade I organised a sort of garage sale amongst my school class. This is not a "thing" in Switzerland, so it took quite a bit of convincing, but I got a permit from the municipality and permission from my school to rent a table (I think) and hold the sale on school grounds, and then talked my classsmates in to bringing their old toys, clothes and books and hanging out for a few hours to sell our things and raise money for a children in need charity (Kinder SOS, perhaps?)
It was, from our point of view, a great success, we raised somewhere over 250 francs. For a 9 year old, a lot of money.
After all was said and done, and I confirmed our totals and told our classmates I would be sending the money off to the charity, one classmate asked if we could donate part of what we raised to WWF. Of course, I said, let's give 200 to Kinder SOS and the rest to WWF. Let's help animals too, right?
She should have raised that before the event, when we were discussing the details of what we were doing and why. The decision had been made and while her idea as certainly a good one, I had promised Kinder SOS all of our proceeds and now had to change those terms.
I should have trained to say no. And she would have trained to organise better, or to present a stronger case (instead of just "let's do this because I like animals", something like "I know we decided X, but looking at what we raised, we can donate Y over here and that will cover this and this...). It would have been a win-win.