1 Peter 3:15-17 reads, “But sanctify the Lord God in your hearts: and be ready always to give an answer to every man that asketh you a reason of the hope that is in you with meekness and fear: Having a good conscience; that, whereas they speak evil of you, as of evildoers, they may be ashamed that falsely accuse your good conversation in Christ. For it is better, if the will of God be so, that ye suffer for well doing, than for evil doing.
A good conscience is one that has nothing to fear because the person so disposed will always do what seems right. Without much forethought, they just know that choice they are making is the right thing to do.  Of course, as already pointed out, this is no guarantee that the choice that is made is the best or the right thing to do.  The good conscience is always followed and thus, protected from being violated or abused. Â
In this text, the good conscience is in conjunction with our good conversation or way of life.  The disciplined life that seeks to please the Father and do His will lives in such a way as to be unashamed. Any sense of shame or guilt is absent from the heart. This is not to say that such as person can claim flawless perfection. Yet, such a one can say that they have done their best, even as imperfect as it may be, to live for Christ.
This way of life does make other people feel uncomfortable, because your life draws attention to their choices that does not reveal the same desire to serve the Lord. These enemies will speak evil of you. When one seeks to be a man-pleaser, he will soon discover that he cannot please everyone without being compromising fence-straddler whose conscience has not been well-guarded. In fact, beware when no one speaks evil of you. When guarding the conscience and seeking to do the right thing, one will always arouse the wicked mind to attack your good manner of life.