The father of a demon-possessed son told Jesus that His disciples were not able to free his son. Jesus "replied by saying to the crowd, 'What an unbelieving lot you are! How long must I remain with you? How long can I endure you? Bring him to Me' " (Mk 9:19). Jesus indicated that the lack of faith of the crowd and His disciples prevented the boy from being freed. In other words, our faith, or lack of it, sometimes makes a big difference for other people. Look at how Jesus healed the paralytic after He saw the faith of the stretcher-bearers of the paralyzed man (Mk 2:5).
Jesus remarked not only about the lack of faith among His disciples and the assembled crowd. He also challenged the father of the demon-possessed boy to exercise his faith. Jesus said: "All things are possible to one who believes" (Mk 9:23, our transl). The father accepted Jesus' challenge and cried out: "I do believe! Help my lack of faith!" (Mk 9:24, our transl.) Thus, the faith of parents often makes a critical difference for their children.
Finally, we are all expected not only to depend on others' faith but to have faith ourselves. Jesus repeatedly says in the Gospels: "Your faith has saved you" (e.g. Mk 5:34). We are saved by grace through faith (see Eph 2:8). Unlike the faith that accepts God's healing, the faith accepting salvation can never be someone's else faith, but only our own faith.
In summary, we are responsible to have faith for ourselves, and often responsible to have faith for our families (especially our children) and faith for others. Be men and women of faith.