I regularly read that we should set our Risk Per Trade at "2%" and only look for trades with a R:R of "2:1".

Why? Who set these figures? How do we determine if these figures are appropriate for our own trading style or risk appetite?

I understand the logic of the two concepts but I am looking for the maths/methodology behind the choice of figures.

Why? Who set these figures? How do we determine if these figures are appropriate for our own trading style or risk appetite?

I understand the logic of the two concepts but I am looking for the maths/methodology behind the choice of figures.