Discussion question – while we are alive, can we be damned?

Since I can’t spell Quaeritur, or whatever it is Fr. Z uses to ask for discussion, I’ll just ask – is it the belief of the Church that a person can be damned while still alive?  I had always believed not – that we always had another chance to get right with God as long as we are on this earth.  But my friend Steve B presented me with a, albeit isolated, quote from Aquinas which states the following:

Catholic apologist, John Salza, points out in his book “The Mystery of Predestination” on pg. 135 that “As St. Thomas teaches, when God withholds His grace as a punishment for sin, ‘God is the cause of spiritual blindness, deafness of ear, and hardness of heart.’ ” (footnote #51 – ST, Pt I-II, Q79, Art 3).

But the Catechism implies rather strongly that, no, God’s infinite Mercy assures that we always have another opportunity for redemption through Confession and penance.  And that had always been my impression – indeed, with my habitual sinning, I probably rely on that belief – perhaps too much.

Could that be wrong?  Did God not harden Pharoh’s heart, so that God’s Glory could be manifested through numerous miracles in the Exodus?  

Does anyone know any other commentaries from Church Doctors on this matter?  Thinking of St. Therese of Lisieux, I can’t believe she would ever feel that God could damn anyone still living (and I think she had a hard time accepting that anyone would be damned, period, so focused was she on Divine Love, although late in life I think she came to understand that many people simply did not have the cooperation with Grace she had).  I have been told that St. Alphonse Ligouri may have outlined thoughts similar to Aquinas, that if we sin severely and habitually God’s Grace could be cut off from us while we still live, thus making repentance impossible.

Anyone have any comments?