I used to grit my teeth and agree to remind them. Now I just say 'why can't you write yourself a note?'
I say this as someone who is apt to forget things. But I've never been one to expect others to remember for me, and nowadays I force myself to be more organised! Surely we shouldn't expect others to take responsibility for our memory failures?
One thing I do say to people is 'If I forget to do x for you, please don't feel bad about reminding me' - but the onus is still on me to remember the thing.