Rate of Perceived Exertion

In the past I have mentioned the use of auto regulation in your training which refers to training "on the fly' but using a set point of load or rep speed to decide how far and how hard you'll push a particular session.

For example you might have a max of 100kgs but you reach 90kgs and it feels pretty heavy. The speed is slow so you have a fair idea that today isn't one for setting personal bests, or even trying them, so you might just do a few extra sets of 2 - 3 reps at 85 - 90% of that 90% and call it a day. 

Rate of perceived exertion is a similar concept but you assign "perceived effort level" to each exercise. You might have used %'s before but this method can be flawed as you would base the %'s off your max, but as described above, your 1 off max isn't your everyday max, so that moderately hard 85% day can quickly turn into a ball breaking 95% day which, in regards to recovery, could stuff your whole week up!

RPE refers to how hard a set feels or how far away you are from failure you are in regards to "reps left in the tank'. For example you might do a set of 5 reps @ 80kgs. After the set you think you could probably have done 7 reps at that load.

The table looks like this:

RPE x 10 = 0 reps left in the tank
RPE x 9 = 1 rep left in the tank
RPE x 8 = 2 or 3 reps left in the tank
RPE x 7 = 3 reps left in the tank with good bar sped and acceleration
RPE x 6 = fast bar movement with minimal effort

So instead of working up to a % of load which can be different each day as described above, work up to a rep number at a particular RPE such as 5 reps at a 9 RPE where you'd finish the exercise when you perform a set at a load that will allow only more rep.

Then move on to your assistance work.

To take this a step further you can assign RPE 's to your other sessions too for speed and aerobic / anaerobic conditioning and include this in your activity load monitoring from last week to again pick up on trends against increased and decreased performance.