I agree with this wholeheartedly. For the longest time I dedicated hundreds, if not thousands of hours to lamenting the past or fearing the future. The notion of mindfulness seemed like an unobtainable ideal. It took me a long time to realise what I spent the most time fearing was situations completely out of my control. Once I started to see this pattern it felt easier to let go.
When I began to read, learn and practice mindfulness as well as pairing this with therapy and meditation - I started to see that I didn't have to rise to the bait with my fears or worries. As I knew where that would send me - down the rabbit hole.
Simply taking in the world around me, slowing down and appreciating what I have helps me to put things into perspective. The supposed needs, wants and desires for what I assumed would make me happy were in many ways a catalyst which was making me feel sad. I guess, the less you want the happier you will become.
It's not to say anxiety and depression doesn't come and go - but when I see what I'm doing, I tell myself to stop adding to it. Simply allowing these feelings to be, and exploring them without a narrative or judgement. To see how they feel and where they feel. Knowing that I don't have to pursue them or stoke the flames any further if I don't want to. I guess knowing that I have control was the most empowering realisation during the years where I was convinced anxiety and depression were holding the reigns. Just as important - to be able to let these feelings go without holding onto them. My therapist pointed out a rather simple, if effective truth - we often hold onto negatives a lot longer and more readily than we do positives.
Ed