Should I force myself to do a thing which my mind does not believe?

It's really not rational for me to do a thing while my mind does not believe it. What does Islam expect from me when it says something is **sin** but my mind does not believe that it's a sin? Does it expect from me to force myself? While I myself would like to try that sin to see the results because that sin is not harmful for anyone in my mind's idea so it's not a sin really. I believe forcing myself does not make any practical advantage for me and causes that I could not find out if it's really sin or not in whole of my life! what's the solution?