Happy St. Thomas Aquinas Day!
Most philosophers view the best possible life to be that which they themselves pursue, and so generally they say that contemplation is the highest human activity. Aquinas has an interesting twist on that. Contemplation is indeed very, very good, but there is something that is better:
The contemplative life is better than the active life that solely concerns itself with bodily necessities; but the active life that consists in passing on to others through preaching and teaching truths that have been contemplated is more perfect than the solely contemplative life, for it presupposes a plenitude of contemplation. That is why Christ chose a life of this type.
The model for Aquinas is not his own preferred activity, but the activity of Christ.