Even so, every healthy (sound) tree bears good fruit [worthy of admiration], but the sickly (decaying, worthless) tree bears bad (worthless) fruit.—Matthew 7:17
The fruit in our lives (our behavior) comes from somewhere. A person who is angry is that way for a reason. His reaction is the bad fruit of a bad tree with bad roots. It is important for us to take a close and honest look at our fruit as well as our roots.
In my own life, there was a lot of bad fruit. I experienced regular bouts of depression, negativity, self-pity, a quick temper, and the chip-on-the-shoulder syndrome. I was harsh, rigid, legalistic, and judgmental. I held grudges and was fearful.