Is there a profitable strategy that works 80% of the time?

yes but noone will give you their for free.

I've always wondered why though. The strategy works, aren't those people already making money off it?

A strategy becomes good when it tunes with the person's instincts and self understanding of the market. You can get a strategy from a person but you can't get the instincts of that person. So you have to make your strategy according to your understanding of the market.

There is no strategy which can assure you of making profit. You have to work hard beside a strategy. Then it is possible to become profitable in this market.

Success of a strategy depends on how you use the strategy. Market sometimes is in a trend and then it goes in consolidate phase. According to the market situation, you have to make change in your strategy and your approach to the market.

Is that your approach?