Christianity is all about transformation. The Lord wants us to take on His own image (Rom 8.29), to become like Him in our minds, our wills, our characters, our hearts, our goals and plans, our emotions, and our attitudes towards all kinds of things. This is what the Bible calls having the mind of Christ in us (Phil 2.5), or having the Spirit of Christ in us (Rom 8.9), or having Christ in us (Rom 8.10). The Christian who does not take on the internal characteristics of Christ is a Christian in name only. Paul said that being Christ-like in our character is the genuine mark of a child of God: “all who are being led by the Spirit of God, these are sons of God” (Rom 8.14) and “Because you are sons, God has sent forth the Spirit of his Son into our hearts” (Gal 4.6).
This does not mean, however, that each of us will become exactly the same in every way. God is not trying to turn us all into robots with no difference between one and the next one. That is because there is a difference between your character and your personality. God wants us all to be alike in character. But in our personalities, we can be quite different.
Your character is the sum of the parts of you that have to do with your moral values, your ethics, the knowledge of right and wrong, and your spiritual orientation (either toward God or toward something else). Your character includes moral traits such as honesty or dishonesty, greed or generosity, meanness or kindness, etc. Your character is objectifiable, that is, it can be measured and evaluated as being either good or bad.
Your personality, however, is subjective. It is the collection of things about each of us that are not moral in nature, but instead are the things that we prefer or the ways with which we are comfortable. For example, some people are shy and some people are outgoing. It is not right or wrong to be one or the other. Some people are quiet and some people are talkative. Some are “Stoic” and some are more openly emotional. Some people like everything to be neat and orderly, but others are comfortable without it. Some people like single flavors, others like them mixed. None of these things are either right or wrong.
In short, a person may have a pleasant personality but have a bad character (think of the stereotypical politician). Conversely, a person may have a good character but be somewhat aloof from other people.
Problems develop when we fail to distinguish between character and personality. First, sometimes a person may be either condemned or praised for having a certain personality trait as if that personality trait were a moral quality. For example, the “neat freak” may condemn people who are not as organized as himself. But personality is not moral, and it is not something to be condemned. Second, and similarly, sometimes we dismiss our character flaws by calling them personality traits. So we might ignore the sins of malice or gossip by saying “that’s just my personality.” It isn’t. Third, another problem develops when we fail to distinguish between character and personality at all. There are two ways this becomes a problem: 1) when we treat every trait as if it were a personality trait (and so moral traits become just as trivial as one’s preference for a certain flavor of ice cream), or 2) when we treat every trait about a person as if it were a character trait (and thus judge or condemn people unnecessarily).
God wants us to be alike in our characters. We should have the same moral values (which are taught by Jesus), the same goal of pleasing God, the same spirit of love for others, the same moral and spiritual purity, the same freedom from selfishness, etc. This is what Paul meant when he said “be of the same mind” (Rom 12.16; Phil 2.2). Of course, not everyone is at the same level of spiritual maturity or Christ-likeness. Some Christians have, because of their maturity, become more pure, more loving, or more humble than other Christians who are not so spiritually-developed. But this does not negate the fact that the same holiness, the same love, the same humility, the same faithfulness, the same virtue, etc. is to be in each one of us, even if these qualities are in us at different “levels” or “degrees.”
However, God has not laid down any requirements about our personalities. It is OK to be shy. It is OK to be talkative. It is OK to like organization, and it is OK to enjoy the thrill of competition. It is OK to enjoy football over reading (or vice-versa). None of these things make you a better, or worse, person before God. But gossip, wrath, selfishness, deception – these are not personality traits. These are character traits, and God will certainly hold us accountable for having them.
Of course, I should always be on guard to make sure that a trait of my personality does not become a kind of selfishness in which I indulge to the harm of other people. In that case, the problem is not with my personality, but that I have developed a character flaw (a failure to think considerately of others). For example, a person might enjoy talking (and there’s nothing wrong with that), but when they talk to the point of interfering with other people, then a problem develops. The problem lies not in the person’s personality, but his character. He allowed something (in this case, one of his personality traits) to get out of control to the hurt of others. Or someone may have the personality trait of being methodical (which again, is perfectly fine), but if he does not control is desire to be methodical and it causes problems for others, then he has shown a weakness in his character in that he is not being considerate.
The transformation of ourselves which is the goal of the gospel of Jesus Christ involves the transformation of our character. We should, each one of us, strive to change our characters as completely as we can to be conformed to the image of Christ. But each of us gets to keep our personality.