Unprompted drive
Drive that arrives without prompting.
Flat can mean physical readiness seldom arrives on its own, or effort leaves you carrying its cost into the next day. The clue is what challenge asks of you and how you recover.

Drive that arrives without prompting.
Steadiness when challenged.
Recovery after hard physical effort.
The distinguishing clue is the relationship between unprompted drive and the cost of recovery, without making a claim about hormone status.