I think you hit it on the head when you mentioned the modern Western (American?) tendency toward only being satisfied with instant gratification. The feelings of satisfaction or dissatisfaction you mentioned are entirely of your own internal construction. This is important because you get to decide how you feel. If you feel a way you don't like, pause, self-observe, then move forward.

Some people will feel highly satisfied having accomplished their outline on day one. Still others will feel satisfied without any regards to how much they got done. After all, to butcher Alan Watts, the point of life isn't to get to the end any more than that's the point of music or dancing. Enjoy each note as it comes, each step in the dance. If you prefer not to enjoy it, that's your choice.

Also, there have been some good studies on delayed gratification and personal success. Here are three:

• Inherent association between academic delay of gratification, future time perspective, and self-regulated learning;
• Delay of Gratification, Psychopathology, and Personality: Is Low Self‐Control Specific to Externaiizing Problems?;
• Rational snacking: young children's decision-making on the marshmallow task is moderated by beliefs about environmental reliability.

There's reference to the marshmallow experiment done in the 60's and recreated in the 80's that first brought this subject to light. You can read about those studies on G Scholar or Wikipedia.