1. You will miss out on many things in life
You may have met that special someone had you gotten dressed and went to that party, instead of laying on your couch. You could you have enjoyed your summer instead of attending summer school, because you were lazy to study for your math exam... it adds up.
2. Not doing it now, means more work later
Just because you're too lazy to clean right now, or finish that research paper that's due next week- doesn't mean it will go away. Instead you'll have a lot more to clean, and a lot more stress/more work to try to get your paper done on time.
3. Life is too short
You are alive today, which means that you should be making each day worth while. Do what makes sense, and try to be productive and happy. It is for your own benefit.
4. Why dream, when you can make it happen?
Why sit around, when you can make things happen for yourself. You want a 6 pack? Go get it! You want to finish your degree faster- work hard and take more courses. What you can control, take advtange of.
5. Realizing things too late
Sometimes we look back and wish we had done things differently... instead of repeating this thought and this feeling of regret- act while you can.