To say NO

My dad told me that when you are able to do charity for others, it means that you are a "rich" person that why you are able to give.

I wonder if the above theory works when it comes to the working world. I am able to help because i am capable in handling additional tasks?

As usual, there is staff turnover monthly, my manager required me to take over some task for the time being until the replacement arrives next month. Anyway it is a simple tasks and i thought it was reasonable. But my colleagues felt that i was a "YES" person and reckon i was bullied. I am not sure if this is sympathy or being sarcastic?

Can this place be a lot less complicated?