Consistency beats intensity every time.  Consistency is much more important to promote growth than intensity is, but if you can do both thats even better.  The key, and this is the self-discipline part, is to take action every day to promote the growth you are looking for.  It is better to spend an hour a day progressing improvement than it is trying to do 8 hours of work every two weeks.  The results will be dramatically different.  So even if the intensity of the work is way less on your daily effort, the growth over time will be significant.  Consistency is the key.

Success isn’t always about greatness. It’s about consistency. Consistent hard work leads to success. Greatness will come. Dwayne Johnson

It's not what we do once in a while that shapes our lives. It's what we do consistently. Anthony Robbins

Success is neither magical nor mysterious. Success is the natural consequence of consistently applying basic fundamentals. Jim Rohn