It means to take a risk by asking for too much or doing something risky after already having some success.

iskušavati sreću, izazivati sudbinu

 

I already asked my boss for one week off. Asking for more this month might be pushing my luck.

He won $1000 at the casino and decided to stop. He didn’t want to push his luck.

My friend borrowed my car without asking. When he asked to borrow money too, I told him not to push his luck.