User blog comment:FairyRaven/Fairy Tail Chapter 370: Demons Reincarnated, Review and Commentary/@comment-7418318-20140207112700

Lamy said it was a blessing for her that Tempesta lost his memory after each of his death'.

Could that mean that the last time she re-assembled Tempesta, Lamy messed up and thus the incarnation of Tempesta that fought Laxus was actually weaker than his true potential?

If she messed up like that and Tempesta got angry and punished her (or intended to punish her once he returned from the mission to kill Yajima) it would explain why it's a blessing he lost his memory to her.