Sorry, if these do not have a Biblical basis, i answered them from my own POV.
A. I believe you have to see how far you are in spiritual poverty you are before you can a Christian. For example, it is often said an alcoholic has to hit bottom.
B. Looking back on my time as a sinner, I definetly believe I wasted a lot of energy. I am saddened how I wasted my life, the excuses I made. Looking back I am mournful for all the lost time.
C. I mourn for the people who have not been saved, for the sins I see on a daily basis that is seen as normal.