It is easy to read Mk 11:22-24 which tell us that we can ask for anything in prayer with faith and we will receive it. We can even it seems tell a mountain to throw itself into the sea and it will be done for us. This has led some Christians to believe that with faith we should get a 100% hit rate on our prayers, if we have enough faith. On the other hand, failed prayer means a lack of faith.
This sounds reasonable if we forget the wider context of Mark's Gospel. I always believe that when we are looking at a verse and seeking to interpret after looking at its immediate context, we need to consider it in terms of the wider document; in this case, Mark. If it is a thematic text like this one on prayer, we need to especially consider what else Mark records on prayer.
In regards this verse 11:22-24 the most important textual link for me is Mk 14:32-42. Here Jesus comes to God in prayer. He has a mountain to move; the cross! He has shown his awareness of what he is to face since Mk 8:31; 3 times referring to the pain and suffering he will face. In the Garden of Gethsemane he sensed that his time was now; he knew that Judas had betrayed him and he knew his enemies were approaching. He pleaded three times for deliverance, for another way. Yet each time he prayed, he stated, 'yet not my will, but yours be done.' Here we have faith demonstrated. The faith talked about in 11:22-24 is not an absolute confidence that the specific prayer request will be affirmatively answered. The faith talked about is a total trust in God that no matter what happens, he is in control; he can be trusted!
Jesus expresses that trust. He asks for the specific request; 'take away from me this cup of suffering.' He prefaces it, 'I know you can do all things'. He follows the request with 'not my will, but yours be done'. So faith is utter confidence in the will and Lordship of God our Abba Father.
So when we read 11:22-24 we need not take off and join the hyperfaith movement which is distorted theology. Rather, we should state our absolute faith in God, pray the prayer request and then let God be God; and allow his will to be done. His will is always best and we can totally trust him.
So if you are praying or have prayed a prayer that did not get a positive result; don't bemoan your lack of faith, don't give up on Jesus for not being true to his word; look to God and trust him; it will work out for the best. It always does, although we often don't see it at the time.
Like my mate who was an international sports star who got smashed in a car crash and is now disabled; he said to me a few years after his accident, 'it was the best thing that ever happened to me!' 'Why?' I asked. He told me, 'it was because I was too selfish for other people before my accident.' I am a much better person for it.
God is in control.