Going about setting boundaries with uncooperative family

Ok so I've started to go home early in social situations like yesterday, we go to my aunty's house for Christmas dinner, I had to leave early because it was all too much. We make our boxing day the day after boxing day so my aunty doesn't have to cook twice in a row.

Anyway, my mother wants me to go to my aunty's again after already going there for Christmas like twice in a week is mentally draining so I said I didn't want to go and my mother said I don't "push myself enough" like I could've said I didn't want to go on Christmas but I did and I want to cry because I'm frustrated, I thought my mother understood but apparently I need to "push my boundaries", what should I do to make her understand if she doesn't already?