Cats (and all animals really) have the innate ability of being totally present in the moment. They don't dwell on what happened yesterday, or what is going to happen next week - I don't think they even know what the concept of "next week" is! They just enjoy life as it comes along and react to it accordingly.
We humans seem to have made life a lot more complicated for ourselves. We worry about things that happened days, weeks, months and even years ago. We overthink things, we agonize over what someone said and what they really meant. Nothing is simple and straightforward because we are too busy adding nuances and afterthoughts.
Sometimes we need to look at our animal friends, at their contentment and their trust in the world around them. They don't spend the day wondering if they're going to be fed, or patted, or let in or out. They just get on with living in the moment, enjoying what comes along (or disappearing if they don't like what's going on). No frustration (or very little), no stress, no depression - just an acceptance of what life hands them.
They aren't out to control and micro-manage their world and we need to learn to do the same. Letting life come to us and taking it a day at a time works for humans as well as cats (and dogs). Learning to relax and releasing the worry and anxiety is when we find freedom and joy and the pressure comes off. Living in the moment is definitely the way to go!