(A journalist asked Mother Teresa if she was ever in doubt. After all, the journalist said, Christ himself had moments of doubt in Gethsemane.)

No. There was no doubt. It was only for a moment that He felt unsure. That was as a human being. That was natural. The moment you accept, the moment you surrender yourself, that's the conviction. But it may mean death to you, eh? The conviction comes the moment you surrender yourself. Then there is no doubt. The moment Jesus said, "Father, I am at your disposal, Thy will be done," He had accepted. That was His agony. He felt all the things you and I would feel as human beings. That's why He was like unto us in all things, except sin."

[If uncertainty remains] that's the time to go on your knees, eh? .... In that prayer, God cannot deceive you because that prayer comes from within you. That is the time you want Him most. Once you have got God within you, that's for life. There is no doubt. You can have other doubts, eh? But that particular one will never come again. No, I have never had doubt.... But I am convinced that it is He and not I. That it is His work, and not my work. I am only at His disposal. Without Him I can do nothing. But even God could do nothing for someone already full. You have to be completely empty to let Him in to do what He will. That's the most beautiful part of God, eh? Being almighty, and yet not forcing Himself on anyone.

(Blessed Mother Teresa, Come Be My Light, pp 259-260)