When family and friends promise you something do they usually come through or back out and you just have to understand?

My mom would always back out. I remember as a child I'd ask my mom to go visit my dog for example and she'd say we'll go Saturday, and then Saturday would come and she'd say that she's tired and we'll go another time. Now I realize that maybe it was a real reason, because she'd work overtime just to make money for us, because we kinda struggled financially, but as a child I felt really let down, and so often. Like sometimes I wished she just wouldn't have promised.
And I think as I grew up, I picked up on that habbit, and would cancel a lot on meet ups.
Now, because I can see the bigger picture, I try not to do it much anymore, so I just don't make plans much, I just do the spontanious "let's go now" thing.