Faith comes by hearing the words of christ.( Romans 10:14-17 )

without faith it is impossible to please God.( Hebrews 11:6 ).

The woman heard christs word which is powerful, and the WORD which she heard was so powerful that it created THE FAITH

Faith can move mountains! 

Wehave to believe that there is Only One God in three Divine Persons, Father, Son, and Holy Spirit; I believe that Jesus, became man, and died for our sins, and that He will come to judge the living and the dead. We have to believe all these and  the truths which the Holy Church teaches, because God has revealed them and He will never deceive nor can He be deceived.

When we ask Jesus to do something for us we have to believe that if it is in compatibility with His Will, it will be fulfilled.   And thanks is offered even before the prayer is granted.