You always want to be lifting heavy enough such that you’re approaching muscular failure. Aside from the deload week, you should only be able to perform another 1-3 reps before ending your set. Since Booty by Bret prescribes the number of reps to complete, scale the load to match the weekly recommended effort (found in “Microcycle” page). A few signs you’re lifting heavy enough: 1. Your rep speed slows down on your last few reps despite pushing as hard as you can 2. You require the full recommended rest period to replicate your strength 3. You have minor form breakdown 4. You’re gaining strength over time