OP I can sympathise
I’m a people pleaser but a few years ago made the decision to stop doing so much as I was affecting my own physical and mental health constantly putting myself out for others.
What surprised me at first it wasn’t an overnight change. It took a full year to really start getting into the swing of saying “sorry I can’t do that”
As PP said start with small steps - I started by saying “no” to easy things eg. Electricity company calls to change tariff - I gave them a straight “no thanks, not interested” from the beginning rather than let them waste my time waffling on. The more.I started saying “no” people the easier it became.
If I’m put on the spot eg. “Can you help out with this on this date” I have a variety of stock answers.
I don;t have my diary on me at moment, can I get back to you?
Hmm that dates rings a bell, need to get back to you on that
Pretty sure we already have something on that day. I’ll confirm later
Get the picture? This gives you breathing space. You can then go back to said person with a yes or a no (you might want to do it!)
I think I’m about 3 years on now from my original resolution and I find it easier every day.
Last night someone was asking why I wasn’t doing something that THEY thought I should be doing (even though they weren’t doing it themselves)
I looked them straight in the eye and said “because I don’t want to”
They were so shocked they changed the subject. The sky didn’t fall in and I felt great!
Baby steps OP - good luck