get (one's) juices flowing
To become inspired to greater creativity, productivity, or energy, or to cause such a feeling in someone. I've been having trouble getting this essay started—I just need to get my juices flowing. I find that a good run first thing in the morning always gets my juices flowing for the day ahead. We've been sitting here for an hour with nothing written, so let's play a few word games to get our juices flowing.