The top 15 procrastination rationalizations

1. Ignorance: "I didn't know I was supposed to do that." 
2. Skill deficiency: "I don't know how to do it."  
3. Apathy (1): "I really don't want to do this."  
4. Apathy (2): "It really doesn't make any difference if I put this off."  
5. Apathy (3): "No one really cares whether I do this or not."  
6. Apathy (4): "I need to be in the mood. I'm not."  
7. Fixed habits (1): "But I've always done it this way and it's hard to change."  
8. Fixed habits (2): "I know I can pull this out at the last minute."
9. Fixed habits (3): "I work better under pressure."
10. Inertia: "I just can't seem to get started." 
11. Frail memory: "I just forgot." 
12. Physical problems: "I couldn't do it; I was sick." 
13. "Appropriate" delays (1): "I'm just waiting for the best time to do it." 
14. "Appropriate" delays (2): "I need time to think this through." 
15. "Appropriate" delays (3): "This other opportunity will never come again, so I can't pass it up."  

Source: Tuckman, B.W., Abry, D.A, & Smith, D.R. (2008). Learning and Motivation Strategies: Your Guide to Success (2nd ed.). Upper Saddle River, NJ: Pearson Prentice Hall.