Low mood help

Hi sisters,
I am wondering if anyone can offer me some ideas or advice regarding low mood. I am 42 years old and have always been a fairly happy and content person in my adult years. Lately though I find I am feeling really flat and low some of the time. Sometimes there is a trigger and sometimes there’s not. I can still function well and smile a lot and find happy moments but I feel this low mood for a couple of days sometimes and then it goes away and I feel ok again. After it, I think “I’m not going to let that happen again” but it seems it still does and is still occurring. I miss feeling normal all the time. I know people have ups and downs but I haven’t felt the downs like this so regularly before. I have recently had some massive changes in my life and wonder if that’s what’s started this.
Anyway my question is- the wait for mental health help is HUGE at the moment so can any suggest somethings I can do when I feel like this to help lift my mood? Especially interested in those who have sought professional help and what the advice was that worked for you as I am months away from being able to access professional help.
Thanks ladies 💛