I have read a few event card management questions and the confused me. From what I understand is that throughout a turn you may draw multiple event cards but durring the regroup phase you only get to play one event card and the rest you drew that turn are discarded. Now when I say played I mean you resolve the effect on the card right then and there unless it is a persistent card that states it remains in play.  So someone who gets a card that gives them a unit for example cannot bank that card for use I the future, he has to claim that unit right then and there. Also sorry for typos iPad auto correct.

Yes, at the end of the Regrouping Phase, ANY event cards that are not played (either placed in your play area or just a one-time effect) are discarded. They cannot be saved for future rounds of the game.

Also, try to remember not to look at the event cards that you receive until the beginning of the Regrouping Phase. Just as the rules suggest on page 14, I tuck the cards under my faction sheet to remind myself not to look at them right away.