I agreed to let him join us, even though it was 'against my better judgment'. [=even though I did not think it was the best thing to do]
In my 'judgment' [='opinion'], the stock has performed badly. = It is my 'judgment' that the stock has performed badly.
“Were his policies good or bad?” “I'll have to 'reserve/suspend judgment on' that. It's too soon to know.”
(..) You want me to take you out of here? Just let you run away? See how far you could get? Why would you do such a foolish thing? On the day of my judgment... ...when I stand before God... ...and he asks me why did I... Did I kill one of his true... ...miracles... ...what am I going to say? (..)1999 The Green Mile