Faith is essential to be born again, to become a Christian, which is free, by grace, only by faith, without any good work or merit from our part (Ef.2:8-9)...
... And it does not end there, faith is essential to live every minute of this life on earth. If Christ is with you, in you!, you have to be in this life full of enthusiasm and joy and love, no matter what happens. But you have to be aware of it and actualize it, trusting in Him, in every occasion or circumstance of your life... in everything, just do your best, and then, trust in God all the way, it is the formula that never fails, the one given by God to Joshua (Jos.1).
If you ever feel sad or worried, it is because at that moment you are in sin, with the devil in you, or you forgot that Jesus is with you. In fact the greatest sin in the Bible is "not to trust in God": In the Old Testament it is called "prostitution against God", St. Paul says, "whatever does not proceed from faith is sin" (Is.1:21, Jer.2:20, Rom.14:23). To trust in power or money or our abilities, instead of trusting in God, is a prostitution against God, it is to throw ourselves in the hands of other, trusting in that other, and that's prostitution!. And this is the worse sin, and the one we usually do not confess.
It is so important to live in faith every minute of this life, that in this chapter 3 St. John repeats it 9 times: "For God so loved the world that he gave his only Son, so that everyone who believes in him may not perish but may have eternal life... Those who believe in the Son are not condemned, but those who do not believe are condemned already"... and ends up saying: "Whoever believes in the Son has eternal life, but whoever disobeys the Son will not see life, but the wrath of God remains upon him" (Jn.3:16, 18, 36)... It is a matter of life or wrath, now!, in this life on earth, and for all eternity. In fact, John mentions "faith" or "believe" 98 times in his Gospel. John is called the Apostle of love, but his Gospel is the Gospel of faith,because only you can love if you have God in you, and the only way to have God is by faith... faith in God in the Old Testament, faith in Christ in the New.
A "Christian", is a person who lives in Christ, in his Church, and Christ lives in him... he lives inside God, and God lives inside him... "it is no longer I who live, but it is Christ who lives in me" (Gal.2:20). It gives me vertigo just to think on it!… Jesus is with you, in you!, right now, but you have to live every moment with faith, aware of this fact, and in every minute of this life… A Christian is "another Christ", to live on earth the glorious adventure of love, being humble and meek like Jesus, doing the same work of Jesus, casting out devils and healing the sick, going about doing good, helping people to go to eternal Heaven, by being like Jesus "the Lamb of God who takes away the sin of the world", to take away all bad karma of people.
... And all of this with fear to nobody and to nothing, because a Christian does not trust in power or money, but lives this present mortal life "by faith in Christ"... and if God is within me, I am not afraid of anybody, because God takes care of me... and I am afraid of nothing, because Jesus is the Lord of the winds and of the tempests and of the hurricanes, and he lives in me.
Jesus tells us that we have to trust God our Father as the birds or the lilies of the field, as little children trust in their father (Matt.6:25-33, Matt.18:3)... a child has nothing, but he has everything in his father that loves him. Never ever a child thinks his father is going to forget to get his meals or dresses or toys... he trust his father!, it is the main characteristic of a child... and a Christian, since Baptism, becomes a child of God, a brother of Jesus, with the same inheritance that Jesus Christ himself (Rom.8:17)... God loves us and cares so much about us that even all the hairs of our head has well counted (Matt.10:30)... anything and everything in our lives are for the good of us!, including sickness, hurricanes, failures, problems in the family or at work... everything is a gift of God for us, planned with care and love by God himself for us (Rom.8:28). If you ever fail on any project because lack of money, start another one a thousand times more expensive!... your Father is the multimillionaire!... if you failed, it was not for lack of money, it was because God your Father did not wanted you to succeed, may be it was not good for you, or will bring you to Hell, He knows better!... you and I are like little children compared with our Father, like birds or the grass of the field... He knows!... and he loves and cares for you!.
A Christian is got to be a very happy person, even in death!... because death is the glorious door to enter Heaven. And by the way, we celebrate the feast of the Saints on the day they died, the greatest day of their lives!.
Suffering must also be a source of happiness for a Christian, because every affliction has a glorious double edge: 1- It is like an injection that God uses to purify him... I am a Medical Doctor and people pays me to give them injections, they may hurt a little, but they are meant to heal a lot. (Read Heb.12).
2- Every pain or sorrow is an individual cross, the best weapon to help relatives and friends to go to Heaven. Jesus did not redeem us with his beautiful sermons, nor with his miracles, but with his cross!... and our daily cross is our best way to be evangelists, co-redeemers with Christ, as Paul puts it: "I am now rejoicing in my sufferings for your sake, and in my flesh I am completing what is lacking in Christ's afflictions for the sake of his body, the church" (Colos.1:24).
A Crippled old Christian lady at home is not a burden for the family, but the best treasure of that home... she is another Christ helping all her relatives and friends to go to Heaven... and Heaven is our home!.
An unhappy person is a bad Christian. He is a Christian without faith, without trust in his Father!. He is worse off than a pagan.