How do you realize loss in Funcamental Analysis

Hi guys, this is my first time posting here, so I apologize in advance if this question does not belong here.

I am trading for few years now and I usually used technical analysis. This group has inspired me a lot to find value trades and invest for long term.

I've been learning numbers around fundamental analysis, some has been working but some are not.

Usually with technical analysis, I know where to have my stop loss and when to exit a trade when its moving sideways.

Whats your approach on value investing that lets you know to walk away from a trade, if to hold it, take profit, or loss. How do you guys usually set a target or a stop loss ?

Thanks in advance, and apologies if this question does not belong here.