I think if you understand your build (not just class) then you should know what counters you and who you counter in those regards For example, if you don’t have a lot of condi cleanse then obviously you should avoid scourge (or any condi build in general). If you can’t maintain a reasonable stability uptime then warrior and holo might give you a hard time. And if you are glassy then power thief and Mesmer (or any power build class) could be your nightmare and so on. Then again it comes down to your skill and experience. Try to avoid direct match up with those who counter you is generally a good practice in PVP. I don’t think there’s any shame in running away from a fight if you know you gonna lose (though you may get abused by other players from time to time). Good luck