If all you have to do is accept Jesus to be saved why do you need to present yourself as a workman?

Well, the answer is you have to do more than just accept Jesus to be saved. So, apart from having faith you need to repent. That requires work. You have to confess the name of Jesus before men because otherwise Jesus will not confess you, so that requires effort. You have to be baptized for the remission of your sins which doesn't really require work from you - just from the person dunking you, really. And you have to stay faithful until you die which is where the workman bit comes in - a hard job sometimes. BTW, faith is described as a work (John 6:29).