Definition of scared money
A player is said to be "scared money" when he or she is playing above his or her comfort level. The English expression "scared money" could be translated as "the fear of losing money". A player who is used to playing on cash game tables with €0.25/€0.25 and who would suddenly be sent to an NL400 table with €2/€4 will probably be scared money, i.e. it will not be comfortable to lose a whole buy-in. A player might be scared money when he is new to a limit. If he moves up from NL100 to NL200, the first few days he plays NL200, he may be less aggressive and more cautious than usual.
Recognize when you are scared money
The limit at which you will play poker will depend on several things. First, your skill level. Second, your bankroll. You don't play NL400 with a $1000 bankroll, it's only 3 buy-ins. You also don't want to play too low. If you play too low, you might not respect the limit and become too aggressive. And if you're scared money at the limit where you're playing, lower the limit. You can't play optimal poker when you're scared money.