But while I do think appreciating what you have is part of how to avoid the hedonic treadmill, I don't think it's a matter of learning to be happy with a routine.
I've found it possible to make a conscious effort to avoid hedonic adapation, and enjoy novel things without allowing them to become a new baseline. If you can maintain your expectations at the same level, while improving your actual circumstances noticeably above that level, you can maintain a higher level of enjoyment of your life.
So the goal is generally to increase your level of happiness - to have a higher baseline in terms of feeling good and having a sense of well-being.
It's futile to chase joy in place of happiness, because each hit of joy makes the next one feel less exceptional.
Although joy feels like happiness, it's not the same thing, and it's barely related. Joy often has to do with doing more. Doing something extra and exceptional to move the needle.
Happiness often has to do with doing less. With being less focused on doing/attaining/obtaining something new, and more focused on mindset: on finding happiness in what we already have.