One of the best pieces of advice my parents ever gave me was to live below my means.

I didn't always do that but for the most part I did.

I consider that policy the main reason I was able to retire early.

I would add now, as far below your means as possible.

Not to make your life miserable but to really consider on what you spend your money.  I do wish that minimalism had come into my life long before it did and I had become less focused on things long before I did.

Someone once told me their definition of "rich" was being able to lose your job and not have to change one single thing about your lifestyle even if you never found work again.