be self-controlled; set your hope fully on the grace to be given you when Jesus Christ is revealed.
Once you prepare your mind, then you may begin to undertake this next step: self-control.
Proverbs 25:28 says, "Like a city whose walls are broken down is a man who lacks self-control." If a city does not have its walls, it is nothing to over run that city. Enemies can come and go, and that city has no chance. Self control works the same way as those walls. It keeps the city firm and sure. In ancient days, you could build up a city as well as you would like, but without walls, there is no firmness to that city. An enemy could be waiting over the next hill and the city would never even see it coming.
Anyone who has truly tried to practice godly self control has probably been overwhelmed by the sheer magnitude of what they were trying to accomplish. I believe that is why Peter threw in this little reprieve before he continued on in this list. He says, "set your hope fully on the grace..." Don't hope in your self control, hope in the grace that has been brought and will be brought through Christ. Don't hope in your prepared mind. Put your hope in Christ. His grace is sufficient.