The Israelites, who had seen the Lord miraculously plague the Egyptians with frogs, gnats, flies, pestilence, boils, hail, locusts, darkness, and the death of the firstborn, did not truly believe in these miracles. If they had, they would have believed that the Lord would do one more miracle and free them from the pursuing Egyptian army at the Red Sea. Instead, they expected to be killed (Ex 14:11).
The scribes and Pharisees were like the Israelites at the Red Sea, for they did not believe in Jesus' many miracles of healing and deliverance. They insisted on Jesus doing more signs, as if the miracles He had already worked were inadequate (Mt 12:38).
We likewise need to believe in the miracles the Lord has already done. Our faith is based on the miracles of His Incarnation, sacrificial death, and Resurrection. Our life in Christ is based on the miracles the Lord has done in Baptism, the Eucharist, and the other sacraments. To live the Christian life, we must believe not only that the Lord can do miracles but especially that He has done miracles.
Ask the Lord to strengthen your faith in His death and resurrection. By His grace, strengthen your faith in being baptized into His death and resurrection. Live on miracles.