Most of our thinking is done in comparison. Something isn't dark. It's darker. It's not light. It's lighter. We look at new things in light of old things and discovering is fun. The surprise of being different from what we expect can delight us. There is so much we don't know that constantly looking for experiences that expand our choices can be a wonderful incentive.
Without change, we can become accustomed to almost anything. Your 50th night in first class on a plane is not the same as your first night. At that point you realise that your bed at home is better than the bed in first class. Airlines charge more for something being less horrible. Closer to what you get on the ground. Think how delightful getting a clay mug on a plane would be and then look how many you have in your cupboard. A real, actual, metal spoon. Luxury. You tell the kids of today, and they won't believe you.
One implication of this is that happiness can actually come from making things simpler most of the time. Making things less pleasurable. Not horrible, but unremarkable. Then occasionally do something amazing. Our minds are largely just a bunch of memories. Memories come from stories. Stories are mostly about highlights, and the way they end. Daniel Kahneman calls this 'Duration Neglect' and tells of experiments where patients talk about the pain of procedures. Their memory is not of the average pain. They remember the worst point and the last point.
One story I like to think of in terms of managing going back to things we like (but not often enough that we get used to them) and experiencing new things comes from Intel. Moore's Law is the idea that that chips will get faster and smaller at a consistent rate (doubling every two years). This comes from the number of transistors and the microarchitecture. Intel alternates which one they focus on. Every tick represents a "Shrinking", and every tock represents a "Redesign". This has helped them keep up with the incredible increase in power of computers. I can still remember my first black and white family computer. We used to smash the hell out of the left and right arrow keys playing a game based on the Seoul Olympics. Games are a tad more advanced today. You tell the kids of today, and they won't believe you.
I like 'Tick/Tock' for a few things. I try follow Joshua Foer's advice from 'Moonwalking With Einstein' to go back to books that I have read before. Tick. To savour the ideas in them. The same way someone who is religious savours verses in their Holy Book. If an idea is really profound, you need to chew on it. Not just taste it. Then I will try new books. Tock. I read more than one book at a time, and what I read depends on my mood, but the idea normally applies to which books get added to the pile.
Another Tick/Tock philosophy can apply to coffee shops, restaurants, running routes, etc. Ticking and tocking between things that are familiar and things that are new prevents you from getting used to things, and exposes you to new things. The best of both worlds.