be wise as serpents and innocent as doves. 
~ JEsus of nazareth

Aquinas on desire

Whatever one desires [s/he] desires under the form of it being good. If something is not desired as the complete good [i.e., happiness], which is the ultimate end, then it is desired as tending into the complete good [est ut appetatur ut tendens in bonum perfectum]

ST I-II, q. 1, a. 6