I think you are on the right track, may I lead you in over this way :)
booking a holiday as something to look forward
The problem with that is you are setting a condition to your happiness…. “I’ll be happy when I’m on Hols”
So you are right to look for smaller daily things that are NOT (edit) “far” off in the future.
I’ve very much enjoyed practicing, Gratitude.
And I really mean that as a practice or exercise (daily, hourly, whenever you feel like it) Practice being Grateful.
You’ve said you haven’t anything to MOAN about, take that one step further….. be Grateful for them, let them fill you with happiness and joy.
But it doesn’t have to be “big” things like wife, kids, dog, warm/dry house … it can and maybe should be the small things … bird song, warm socks, nice cuppa….. As you enjoy them, have gratitude for them.
It’s working wonders for me
Look luck, have fun