What Does Truth Have To Do With It?
I hate to break to the world and some believers but while love is an important part of Christianity it is certainly not the only part of it. We don't define it properly when we talk about it. Therefore, most assume it just good feelings.
One Corinthians 13 talks about what some would consider good feelings but people miss what Verse 6 says. Love does not delight in evil but rejoices with the truth. When people accept the ideas of candy-coated and self-centered Christianity, they will get angry or fall away when those expectations are proven false. They accuse those who point out the falsehood of legalism. However, real legalism is about trying to gain favor from God with our external performance.
The heart's subjectivity is what makes it deceptive as Jeremiah mentions. We are often blind to the consequences of our poor actions because we don't perceive them as such. Proverbs warns twice there is a way that seems right to a man but leads to death because it is that urgent. This is why the emphasis on heart change is so challenging.
A more balanced approach to the typical self-esteem narrative is Romans 12:3. "For by the grace given me I say to every one of you: Do not think of yourself more highly than you ought, but rather think of yourself with sober judgment, in accordance with the faith God has distributed to each of you." ( Emphasis mine) I have learned to take caution following my doctrine and conduct. It makes me aware of my weaknesses If Peter saw himself accurately he would have taken Jesus' warning of the devil's test seriously. It would have hurt no matter what, but it wouldn't have come as a shock.
We have emphasized love at the expense of holiness so much that most people have a skewed view. We need both so that everyone can see it accurately.