Playing with scared money would typically lead one to make -ev decisions, which is why the phrase exists. It also means you are probably not playing with sound bankroll management practices in place, and would be much more prone to going bust.
How would you feel about being in a hand for your entire net worth in a coin toss situation but one in which you have a decent amount of fold equity if you shove? How would you feel about the same situation if it was for 2% of of your poker bankroll?
Both spots are a +ev shove in poker terms, but one of them could ruin your life while the other is basically inconsequential.
If you are playing poker outside of your bankroll and can still make +ev decisions, you may be able to gamble your way up the ladder with an edge but it's still gambling. This is what shot-taking basically is... and as the name implies, it's a bit of a controlled gamble even if you have sound bankroll management in place and a set stop-loss threshold.
Basically, in my experience, the best poker players are the ones that are able to dissociate the money from the game and purely focus on making the right decisions in each spot. If you are not able to push your small edges for fear of losing your stack, then you are not playing optimal poker.