It is good advice when you are told to do one thing at a time. But I think that is a bit limiting. That's because some things can never be done with. For example, I am a businessman, and until the Lord calls me, I will keep being one. There won't come a point where I will "finish" being a businessman. However, my being a businessman doesn't also stop me from doing other things. Do you remember when we started upper primary, we used to solve single equations until we got to JSS and started solving two, three, and four equations simultaneously? Good! As times go by, you need to be more sophisticated in how you go about what you do.