A well-intentioned person who prays about a decision can, through no fault of his own, conclude in error. The desire to do God’s will does not necessarily entail the understanding of God’s will. God is certainly infallible, but we are certainly not, and neither are our prayers, and neither are our inspirations.
St. Paul warned the Thessalonians not to be deceived by a spirit that claims to know when Christ will come again (cf. 2 Thessalonians 3:2), contrary to what Christ himself had taught us: that “you know neither the day nor the hour” (Matthew 25:13). St. Paul encouraged his followers to resist all such spirits and to “stand firm and hold fast to the traditions that you were taught” (2 Thessalonians 3:15).
The Spiritual Exercises of St. Ignatius do not give us a method for casting aside the parts of revelation that we never really liked, or for formulating the better ideas that we think should have been there. On the contrary, St. Ignatius gave us exercises designed to strengthen our legs and our arms so that we may stand firm and to hold fast to the traditions that we have been taught, the truths of the faith that were revealed once and for all by Christ to His disciples, concluding with the death of the last of the apostles. Let us keep the faith, come what may.