Read Psalms 90:12  Although this verse is not at the end of Chapter 90, it is the conclusion of all of the verses that we have read already.  Because God is eternal in verse 2, because God is outside of time in verse 3, because our lives are soon over in verse 10 - David asks God in verse 12 to teach us to number our days.  We need to realize that we only have just a few days to live.  We had better use our lives for God than to waste them on useless things.  And the reason that we should be careful and number our days is that so we will be able to live a wise life: so that we will live lives pleasing to God.  Do you want to obey your parents?  Do you want to obey God?  If you do, ask Him to teach you and to direct your life.  You will be happy if God is in charge of your life!  Did you like the picture of the old lady and young lady?