The foundational 1st point of TULIP often causes the most problems because of the title that was given. “Total depravity” can cause people to get the wrong ideas about what it teaches, so people refer to it as “total inability,” “righteous incapability,” or even “radical corruption”. The name is not important but what it teaches, a summary of what the Bible says about the spiritual condition of fallen man, is important.
The doctrine of total depravity is simply the acknowledgement that the Bible teaches, that as a result of the fall of man (Genesis 3:6), every part of man—his mind, will, emotions and flesh—have been affected by sin. In other words, sin has corrupted all areas of our being and every thing that we do. It has penetrated to the core of human nature so that everything we do apart from God is tainted by sin “…all our righteous acts are like filthy rags” before a holy God (Isaiah 64:6). Not only is this in Scripture but can be seen all around us in the fallen world.
Understanding that we are hopelessly incapable of doing anything righteous without the guiding hand of the Holy Spirit is key to trusting in God alone, and not ourselves. It also reminds us that we cannot save ourselves through our attempts at righteousness. Other religions are about checking the boxes to find peace, but through Christ the boxes are already checked and we have peace!
I hope this helps you understand otherwise I can only refer you to the psalms which are chocked full of understanding mans condition since the fall.