Do fewer things: get really good at saying no.
To simplify your life, you need to do fewer things. Of course, that's obvious ... that is the definition of simplify. But too often this question is met with advice to do more! "You should meditate", "You should write a better to-do list", etc. could all be good advice to a person, but to simplify one must first start with subtraction before moving to addition or multiplication.
Say NO more
Every time you do something, ask yourself if you really need to be doing that. Does this thing REALLY need to get done? Does it REALLY need to be done by you? Does it REALLY need to be done now? And even when the answers to these are yes, you think about how you can NOT do this thing in the future.
If someone wants to meet with you, do you really need to meet with them? If so, does it have to be in person? If so, does it have to be dinner?
Society pressures are really HARD to overcome
Unless you have extreme Asperger's, you are going to feel very strong society pressure to do things or to conform. Are you spending time making your house spotless because this is the highest use of your time, or because your relative is visiting and you are worried about being judged?
Don't fall into the trap of doing something just because society says you should. Of course, that is easy to say. I can guarantee that pretty much everyone reading this (including myself) will fall into this trap at least once in the next month. So try your best and go from there. Everything you don't do is a victory (it doesn't need to be all or nothing).
Try, try, try to not massively overweight sunk costs
Don't fall into the trap of doing something just because you have been doing it or started it (sunk cost fallacy). Of course, you WILL overweight sunk costs (assuming you are human). Just try to not massively overweight them and try to be cognizant of sunk costs.
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