be in the thick of it

To be very busy; to be in the middle of or preoccupied with something or several things. Sorry I couldn't make it to your birthday lunch on Wednesday, I'm afraid I'm really in the thick of it at the office right now. Even when you are in the thick of it, try to take a moment each day and take a deep, calming breath. I'm kind of in the thick of it right now, chasing two toddlers around. Can I call you back later?