In exercise, as in controlling your weight, success is the very best motivator. Once you've followed this program through the Introductory Ladder onto the Lifetime Ladder, you will be able to look back on your early steps and find it hard to believe you ever could have found progressing up the lower rungs challenging at all.
Progress in this program is so dramatic I recommend, on occasion, that you take the time to repeat the exercises for a rung five or ten below your current level. Remember when you found that hard? Can you imagine ever wanting to be that unfit again? Certainly not, especially since the time and effort to maintain your current rung are no more than you were spending to attain that much lower rung.