I think one issue with Booker is that when he drives he never seems to dunk in traffic. 3-4 times last night he beat PB or George got to the rim and then missed a contested layup. In the playoffs you don't always get the foul call. he's not strong enough to body the defender away like George without getting called. if he can consistently make the floaters over the top, like Curry, then do it. If not you have to, under control, attack and dunk. Even in the playoffs if you get hammered trying to dunk, you will usually get the call.
I do think Beverly is in his head but I think the biggest issue is the Clippers are attacking him on defense, he's had foul trouble and they've just gone after him pretty relentlessly on that end because he has not been able to play with fouls, he just concedes buckets.
Great player, learning experience.