information on what or who changed you from a losing trader to a profitable one

Things that have worked for me:

1. Moving to higher timeframes
2. Executing more mechanically
3. Having + sticking to reasonable money management.

I actually went from profitable -> unprofitable when I went to much lower time frames. I haven't been able to make anything shorter than 1 week time frame trading work.

What's worked best for me so far is buy + hold using various strategies (for instance, though a simplified all-weather with ETFs). Arguably that's not "trading" but investing.

I also traded options, selling premium for about a year and half based on a mixed discretionary system (meaning, I had a system - it was manually executed but I could decide to take off trades when things looked "too" dangerous). It was short premium so had all of the risks of being short premium.

"The Options Trader Hedgefund" explains a lot of those sorts of strategies. It worked OK but scared the crap out of me.
Arguably I wasn't diversified enough. I didn't beat the S&P but did make ~ 20+% that year.

Arguably it would work in steady down/up markets as well as sideways markets but might have large losses in choppy down/up/violent markets.

Things that have worked for me:

1. Creating a trading plan before every session
2. Creating my long or short bias for the session based on hourly and daily charts
3. Executing more mechanically at specific pre-defined key levels in the trading plan
4. Sticking to a stop loss of 10-12 ticks per contract.
5. Having a pre-defined max daily loss limit

Richh 

information on what or who changed you from a losing trader to a profitable one

Mechanical things: Not moving my stop out of the way, I realized I was doing that and just wishing, and instead of losing a little money and getting out with a little loss and waiting for the next trade, I was letting one bad trade wipe out a weeks worth of winnings.

Mental things: Realizing that I was addicted to the thrill of being in a trade, and the desire to get in was overriding my knowledge of when to stay out and losing me money. Once I fixed those two things, I was then on the way to break even. I added in a commercially available indicator and it was off to the races.

Thanks for the replies, being more specific I am interested in trading crude oil futures thanks for all responses and would like to know the commercial indicator that was mentioned.

What changed me was not one thing but many things
1. Accumulated experience
2. Learning to code and math behind the indicators to understand what they do represent and what they do not
3. Doing considerable back-end research and testing of ideas
4. Reducing account size and number of trades per trade day.
5. Making rules against carrying non-hedged positions, those later got redundant as I forego on trading anything higher than 1 min tf

This is not to claim that I'm some sort of consistently profitable trader but it has overtime helped and overall going in right direction as I've +days more than -ve ones.

There wasn't one specific individual who helped, but there has been lot of learning taken from other traders, one of the many examples would be journals here. I'm also present in number of trading communities in my local market and they usually share their trades EOD, so it helps in long term, even if many of them just bragging or worse faking it. You learn from not just success of others but also failures. Also, I like to look at charts posted by others and analysis they have done on it, it helps you understand different thought process of people. I've many occasions where two different people have two completely contradicting opinions on same chart, which one was right after action is completed is very fun thing to find out, you know?