Think of it this way: the worst way to adapt a program is to add stuff in. That almost never works unless the person has great recovery capacities (or a lifestyle conductive to easy recovery)... and even then, that normally works only for a brief period of time.
So normally when you adapt a program you must trade stuff in and out. So it becomes a matter of spotting what you can take out without losing too much. But what you take out has to be equivalent (or close to it) than what you add in... You can't take out biceps curls and add in squats, both don't have the same overall impact.