Believe in Him brings the fullness of life to all. Having faith and believing in Jesus, the Son of God, brings richness to life.
Many people doubt in Jesus or do not believe at all in Him. There are many other people who do not doubt in Jesus and totally believe in Him.
The difference between these people of how they view life is totally different. The difference of how they view life can be seen when they face illness, death of a relative, family problems, broken relationships, etc.
Believing in Him and having faith in Jesus helps you to overcome these difficulties, to be able to live them through His love, and always to love your neighbour.