New England hit the field at Georgia Tech for the first time since landing in Atlanta earlier this week ... and Tom was as cool as ever during the workout.

In fact ... the 41-year-old seemed downright giddy -- laughing and smiling throughout the practice.

Begs the question ... what is he so thrilled about just a few days before yet another pivotal game in his 19-year career??

Perhaps it's that Rob Gronkowski was healthy and on the field practicing ... or maybe he's just that confident about a victory over the Rams????