for it is written: "Be holy, because I am holy."
As any good counselor would do, Peter backs up his statement from the scriptures. This holiness thing isn't just some brilliant idea that Peter came up with, it is part of the big picture plan that God has for His people.
These last few passages would work very well in a counseling situation (or a discipleship situation, if you prefer that word better). It is a great "blanket statement" that could be used in any situation.
We are to be holy in all we do, because our creator is holy. This applies to your work, your play, your leisure time, your family life, what you eat, what you drink, what you watch, etc. He is a holy, set apart God, and He wants us to enjoy the benefits of life with Him, but we cannot be where He is unless we are also set apart. This is a process that begins with salvation, continues through a sanctified (and sanctifying) life, and is completed at death in our glorification.