What is the single, most effective piece of financial advice you've ever received?

"Invest at least 10% of your money in your education and development."

 

I haven't read this, but it seems relevant to the OPs question:

http://chatwithtraders.com/the-one-thing/

*Note: It's an ebook requiring an email signup.

 

When I was very young my uncle told me "Save every penny you can while your earning power is the greatest". And now I'm the miser that he was!

 

Wrong for a penny. Right for a pound

 

It would be well for a trader to consider this...."You can't eat like a bird and shit like an elephant."

 

The idea that there are earning plateaus.

Roughly 50k, 150k, 300k, 1m, 3m, 10m.

And that moving from one plateau to the next usually takes doing something different or acquiring a new skill. Not just doing the same thing better.

 

That's a more lively, illustrative, version of what Achilles28 said.
"Wrong for a penny. Right for a pound"

 

Never risk more than 2% of TLNW (Total Liquid Net Worth) on any one trade/idea.

 

Always avoid margin calls.