I'm like this both in work and outside. For example, I usually do a four-day week, but lately work have been asking me can I do some work on a Wednesday, my day off. Last week a colleague was sick and I was happy to help out. They've asked me again this week now, just because it's busy. I did say no but am feeling guilty and probably won't even enjoy the day off now! I've no children, but because of a long term condition, although not serious, I don't want to do 5 days any more.
How can I become someone who just says no and doesn't ruminate over it afterwards? I do suffer from anxiety, which probably doesn't help.