There are no rules to risk. You can risk whatever you want, risk from 1% per trade to 5% per trade, if you like you could even treat it as a gamble and risk 50% per trade..

Personally, I do take fairly big risks with anything I do, so for me it makes sense to use a risk in forex of 5-10% per trade.

Now normally we risk in terms of percentage.

Let's take a $100 account.

At a 2% risk of your account, you only lose $2 at max and your trade is done.

$4 at 4%, $1 at 1%. You get the picture.

If you're wondering how to do this with a stoploss, here's a simple formula:

(Account Balance x Risk Percent)/Stop Loss (in terms of 5 digits) = Lots

By in terms of five digits, I mean 12pip stop loss is 120.

Example:

Account: $100

Risk: 2%

StopLoss: 20pips

(100 x 0.02)/200 = 0.01

So by this equation, you would use a 0.01 lot size and with a 20pip SL, you would only lose 2% of your account.

A key thing in risk management is comfort. Play around with the equation's variables. Namely the risk percentage or lot size. Play with it until you find a comfort level.

The old adage is 2% at max. I believe you can get flexible with that number depending on who you are but at like 10% I will 

start to fear for your account.

One more thing.

Risk to reward ratios.

A killer win rate like 90% means jack shit when the RRR is 1:9 (reward:risk)

Even when you win a lot, the 10% of the time you lose, the loss is killer.

When you see successful traders, most are trend traders with high RRR because they ride long trends.

Huge RRRs like 5:1 allow you to lose often but when you win, it basically will cancel out all the losers.

(I'm not saying other traders like swing, tops and bottom pickers, scalpers, etc. can't be successful. They most certainly can. I'm just preaching some risk management stuff for yaa.

So in summary:

- Big RRR so you don't have to worry about always being right

- Use the equation to control your lot size. Your lot size controls how much you lose in a single trade and what percentage of your account that is.