When someone says something is according to their faith, or your faith, what does that mean? It means that something is in accord with the person’s understanding of what God wants, based on actual reasons.
For example, when Alma and Amulek were bound, beaten, and starved for many days, they prayed to God:
...O Lord, give us strength according to our faith which is in Christ, even unto deliverance. And they broke the cords with which they were bound... (Alma 14:26)
What he meant was “God, because of what we know about Christ, and how we have lived, we have reasons to be confident that you will now give us power to break these cords.”
Miracles happen according to the faith of the individual: the individual possesses reasons, belief in those reasons, and action according to those reasons that exceeds what others are willing to obtain and act upon.
A specific example of this principle is given in Helaman, the prophet general, and his soldiers. They were taught that “those who were faithful in keeping the commandments of the Lord were delivered at all times,” (Alma 50:22) and they believed it!
15 And this was their faith, that by so doing God would prosper them in the land, or in other words, if they were faithful in keeping the commandments of God that he would prosper them in the land; yea, warn them to flee, or to prepare for war, according to their danger;
16 And also, that God would make it known unto them whither they should go to defend themselves against their enemies, and by so doing, the Lord would deliver them; and this was the faith of Moroni, and his heart did glory in it; not in the shedding of blood but in doing good, in preserving his people, yea, in keeping the commandments of God, yea, and resisting iniquity. (Alma 48)
Critically, these soldiers did not merely say they believed that those who were faithful would be prospered by God. Part of their reason to believe they would be protected was their knowledge that they had been perfectly obedient to God’s commandments: “Yea, and they did obey and observe to perform every word of command with exactness....” (Alma 57:21) Because of their faith, they were miraculously preserved:
21 ...yea, and even according to their faith it was done unto them....
26 And now, their preservation was astonishing to our whole army, yea, that they should be spared while there was a thousand of our brethren who were slain. And we do justly ascribe it to the miraculous power of God, because of their exceeding faith in that which they had been taught to believe—that there was a just God, and whosoever did not doubt, that they should be preserved by his marvelous power.
27 Now this was the faith of these of whom I have spoken; they are young, and their minds are firm, and they do put their trust in God continually. (Alma 57)
Faith requires you to find beliefs supported by reasons, and to act according to those beliefs.