Thanks OP for his initial question. I hope I can bring something new in to the discussion.
For me, simple living means less choices, more freedom and a clearer mind.
Let me give you an example. Mark Zuckerberg - as controversial his personality and Facebook is - made a great statement why he is wearing the same grey t-shirt every day:
- Source"I really want to clear my life so that I have to make as few decisions as possible about anything except how to best serve this community.
"I'm in this really lucky position where I get to wake up every day and help serve more than 1bn people, and I feel like I'm not doing my job if I spend any of my energy on things that are silly or frivolous about my life, so that way I can dedicate all of my energy towards just building the best products and services."
I think if you have so many possibilities in front of you, the opportunity costs are so high that you feel stuck in a gridlock where you just can't get out of. This makes you unhappy, this makes you think about unnecessary decisions, you will loose a lot of time, and so on.
I think Zuckerberg's t-shirt - as trivial as it may sound - can be used as a metaphor, used in different aspects of live.
Therefore, reducing the amount of time I use for decisions which are unnecessary, have high opportunity costs and don't help me to become a happier person are the incentives for keeping the simple live.