How can I determine if I can really do a job or if I'm dealing with my own biases?

I have worked for several temporary employment services, I have encountered employers and co-workers whom have said that I work fine in non- traditional jobs where there is heavy lifting, then slow down. I do remember still working and co-workers sitting. Later, co -workers would tell me that I did out them and it was hard to admit it. I have worked hard all my life and have done many different jobs through the temp services and aware of the attitudes of several of the companies that use them. I am a native Nebraskan, born and raised most of my life here. Omaha is making transitions, but there are still a lot of conservative, traditionalists. This leaves me questioning, can I really do this or am I delusional? I've studied human biology and did some nursing. I am aware of the different limitations based on gender. Traditional teaching verses individuality.

"I do remember still working and co-workers sitting"

I think you may be a bit niave. In the company I work for, we too say, the agency staff are doing it better than us, too his or her face, as for too reasons, it motivates them enough for them to carry on with the tasks we don't want to do, and because, you do the work we don't want to do.

As we say, why do the hard work, when the temps can do it for us, and we still get the credit.