In grief it is easy to read about how faith affected or effected many things. However, the word “faith” is used several ways, and they do not mean the same thing.
First, “faith” is used to describe hope or belief. When someone applies for a job and someone else says "I have faith you will get it" they are talking the first type of faith. Alma encourages people to have this kind of faith when they experiment upon the word, to just try to give it a place in their hearts.
Second, “faith” is used to describe the spiritual process by which one reaches through to the other side and connects with the power of God. It involves the first kind of faith, but it is something more (as there is a connection leading to the repeated comments that you can't have faith in things that are not true -- you can have type one faith but not type two faith in things that are not true).
Third, “faith” is used to describe experienced based understanding that does not rise to the level of knowledge. I.e. I have faith that the sun will rise in the morning or I have faith that my cat really loves me.
Finally, "faith" is used to describe the calm belief that results from the spiritual process of reaching through and connecting. It is the calm hope and peace that many in grief have following their prayers.
In understanding faith we need to realize that just as the Greeks had words for different kinds of love (such as erotic, friendly, parental, etc.) we need words for the different kinds of faith in order to understand faith better.
Also, it helps to understand that anger interferes with all kinds of faith. In my own life I've found that when I was angry the Spirit couldn't reach me. It came to me as we were studying in Sunday School today and the teacher remarked that Joseph Smith had the same experience of being unable to hear God when he was anger, and that it wasn't until he let go of his anger that he regained contact with God.
As Joseph put it in describing his experience "when the heart is sufficiently contrite, the voice of inspiration steals in and whispers."
I've had many issues as I have dealt with my losses (and seen many others with loss deal with their issues), and for a short time anger as a block to faith and to the whisperings of God was an issue for me. Then, when I was contrite, the Spirit began to whisper to me. I still had to rebuild myself, spiritually I was weakened from the experience, but but faith was there to restore me.
Paul warns against letting bitterness spring up, and I am certain that anger is a stem of bitterness, and one that harms our faith, in all the ways faith can be a part of our lives.