That God has promised and has given His Holy Spirit to the Catholic Church forms part of our faith. As Catholics, we know that the fullness of Truth is found in the Church founded by Christ.
We do not doubt that the Holy Spirit guides and guards us.
But, here is the catch. People must be willing to be open to the Holy Spirit. They must be willing to pray and listen.
Two friends of mine have tremendous gifts of discernment. They share with me many movements of God in the world. I can trust them because they are absolutely orthodox and obedient to Mother Church.
That is my guide to trusting people. If I see that someone is not following the Church's teaching on an issue, such as contraception or ssm, I cannot trust that person's discernment.
A friend asked if someone could go to the "independent" so-called Catholic Church across the river, where Latin Mass is said by a priest who is not under the bishop.
I answered emphatically, "No."
If one removes one's self from the mainline Church, one is no longer protected by God. Why?
The obedient are protected.
I know several saints. Most of them are in Europe. These are women who pray and have conformed their minds to the mind of Christ.
I can trust them. And, if they make a mistake, they repent immediately.
Signs of obedience are signs of holiness.
Do not let go of the life of the Holy Spirit in the Church.