In business there are rules. 

Take lunch for example. 

If you’re invited for lunch, you don’t pay. 

If the lunch is on home territory, you pay. 

If you offer to pay, you pay regardless of who should pay. 

Those are the rules. 

If you end up paying when you shouldn’t pay, it’s not the other guy’s fault. 

It’s your fault for now knowing the rules. 

Know the rules.