Tim Harford has a neat piece in the Weekend FT about how important it is to say no.
“… every time we say “yes” to a request, we are also saying “no” to anything else we might accomplish with the time. It pays to take a moment to that about what those things might be.”
It’s much easier to say yes because nobody gets offended but also because you underestimate the future commitment that saying yes might entail. A psychological trick you can play on yourself is to ask yourself whether you would say yes to something if you had to do it immediately. I actually try to do this if I get invited to do a talk — I ask myself would I drop other things and do it tomorrow?
The thing that Tim doesn’t cover is how to say no nicely which I think is a real art. I’ve had a lot of people say no to me and some do it in a way that leaves you feeling good about the experience and others are just quite rude. Maybe how to do that is a post for another day.