I've already made reference to this but it bears repeating again and again.

The Secret to changing your life to the better is to have more of the good than the bad.

In terns of Finances, spend less than you earn. In terms of Physical fitness, spend more calories than you eat, and in terms of Spiritual growth, spend more effort on your relationship with God than your relationship to the world.

“Personal finance is easy. It’s simple. There is one fundamental law that governs your money. If you master this, you have mastered the entire game: To gain wealth, you must spend less than you earn.”
In David Copperfield — one of my favorite books — Charles Dickens wrote:

Annual income twenty pounds, annual expenditure nineteen six, result happiness. Annual income twenty pounds, annual expenditure twenty pound ought and six, result misery.

That’s all it takes. Think of it another way. Think of it like an arithmetic equation:

[WEALTH] = [WHAT YOU EARN] - [WHAT YOU SPEND]

If you spend more than you earn, you are losing wealth. You are accumulating debt. You are heading in the wrong direction. However, if you are earning more than you spend, you are accumulating wealth. The greater the gap you can create between earning and spending, the faster you will accumulate wealth. There are only two things you can do to gain more wealth: spend less and earn more.
--The Most Important Money Tip ∞ Get Rich Slowly

It's not complex but that old article on Get Rich Slowly nails it pretty well.

Get your balance sheets out.