From "Prayer: The Key to Salvation" by Fr. Mueller, "God must therefore have given man an infallible means [prayer], by the use of which he can preserve his innocence, and by the neglect of which he will certainly fall into sin".

"True prayer, prayer offered with the requisite conditions, is infallibly efficacious because God has decreed that it shall be so, and God cannot revoke what He has once decreed." from: "Providence" by Fr. Reginald Garrigou-Lagrange, O.P.

Comment: Vatican 2 must be able to be solved certainly without question by the use of prayer, and if there are various doubts and confusions, it seems like more and better prayer is needed. Something has felt like it's missing all along, and I think this is a part of the puzzle. The spiritual life must be developed to a greater degree...