@Raelonus overwhelming him because it was his first time experiencing it. It made him more aggressive at no point was he mentally unstable just insecure & didn't know how to deal with it.
Every time someone unlocks Conqueror's Infusion, it was through the heat of battle.
You can't train someone to unlock it.
Rayleigh didn't teach Luffy
Mihawk didn't teach Zoro
Harlod didn't teach Loki
It had to be through their own intuition. Sanji's case won't be any different