Friend who is scared with heavier weights

How do you get a lifter to be more comfortable under heavier weights? For example, I had my friend doing some doubles. I have him report an RPE just so I can gauge how hard it was. He reported the RPE as a 9, but it looked like an RPE of 6. I think he is just scared of heavier weights. How do you account for this in your programming?

He just needs to practice being under heavier loads and lifting for lower reps.
Doing a Sheiko program would do the boy some good :)

Using bands/chains, and reduced ROM like board press or block pulls really helps mentally with higher intensity weights.