Same with me. Whether the results are positive or negative, profits motivate you to do better and losses on the other hand are devastating initially but ultimately work as a negative motivator to do even better to avoid them in future.
The broker must be trustworthy first of all. Then you gotta check on its trading conditions like the commissions, spreads,order execution, leverage ,withdrawal processing time etc and compare them with others to arrive at a decision.
You are right. Novices have a tough time dealing with losses but they should understand that losses are a part of trading and should rather learn a lesson from losses and try to eradicate such reasons for losses in future.