Why are our Prayers Hindered?

James Boyce in his sermon over Romans 1:13 had 6 qualities that can hinder our prayers.

1. Unconfessed Sin
2. Wrong Motives
   
3. Lazy at Praying
4. Idles in the Heart
5. Stinginess
   
6. Unbelief
   

Every point hit home with me (hence why I really liked that sermons I posted it a few entries back). I have much to work on in every point but the last 2 are probably the most glaring to me. What about you?