The quality of the fruit of any tree depends on the root system of the tree. When the roots are growing in deep, rich soil full of nutrients, the tree will be strong and healthy. The fruit of that tree will be juicy, sweet, and resistant to bugs and parasites.
The tree rooted in poor quality soil will have little nutrition to carry up through the trunk to the branches and leaves. The tree will be weak and susceptible to disease.
The quality of its fruit will be poor. We could return year after year and pluck the poor fruit from the tree, but that would not change the health of the tree. The tree would remain sickly and vulnerable, bearing bad fruit. The only way to cause a tree to produce good fruit is to attend to the roots. To make application to our life, if we address only the visible problems or our bad feelings (fruit), we will soon return to these problems and feelings in a short time.
What we see as a problem (lying, stealing, anger, pornography) is not the real problem; it is a symptom of the real problem. There is a problem to deal with deeper down in our tree of life. That something has caused our fruit to be bad. We must address the root system because that is where the problem that we see truly begins. We need to deal with our anger, stealing, or depression by attacking the real causes (roots) in a biblical manner. We have to deal with the heart of our problem in order to overcome it. Note that the root system is equal to the heart. For example, if we have the fruit of depression, we have focused our heart on our wants, our perceived needs, our personal rights, our beliefs, and our desires. This results in a self-centered idolatrous heart, which is revealed by our thoughts, words, and actions.
The quality of the fruit of a tree is determined by its root system, and similarly, the condition of our heart will be visible by our words and deeds. If the roots of a tree are sunk in fertilized ground that is enriched and full of nutrients, the tree will be strong and its fruit will be good.
If the roots are sunk in bad soil and fertilized with poor quality additives or none at all, the roots will have little nutrition to carry up through the trunk to the branches and leaves. The tree will be weak and the quality of its fruit will be poor.
Let us use whatever issue(s) we identified in the question above as fruit. Going back to the reasons why fruit is either of good or bad quality, we must conclude that there is a problem to deal with deeper down in our tree of life. Something has caused our fruit to be bad.
We must return to the root system. In the case of humanity, we can say that the root system is equal to the heart.
What this means is if we have the fruit of anger, depression, anxiety, immorality, drug or alcohol abuse, lying, etc., it is because our roots are embedded in a heart that is not focused on glorifying God. Instead, it is focused on our wants, perceived needs, personal rights, beliefs, and desires. When our heart is not focused on Him but instead is focused on something else, God calls that idolatry.