I use my stop loss as a way of structuring my trade from the very beginning. When I develop a strategy, I collect an inordinate amount of data around every single set-up/entry that I find during a certain time period. From the entry signal to the exit signal I will track how many ticks against me a trade will go before it starts to show a profit.
I take all of those data points and make a histogram, making it easy to see where the most heat settles before turning back into my favor. I will use that as a way of determining what the probability of my trades being profitable should be.
Say 60% of my entries don't trade more than 50 pips against me before turning profitable. If I have a favorable risk/reward ratio (edge) then I would set my stop at say, 54 to allow for a little slippage and sleep at night knowing that 80% of my trades should be profitable, and that I have an edge in my trades.
If, however, I had to put my stop loss at 600 pips in order to get a 90% probability of being in profit and my profit target was only 50 ticks, then you certainly wouldn't want to be in the trade.
There's just some quick examples of how I use stop losses.