Prayer is a vital necessity. Proof from the contrary is no less convincing: if we do not allow the Spirit to lead us, we fall back into the slavery of sin. How can the Holy Spirit be our life if our heart is far from him?
Nothing is equal to prayer; for what is impossible it makes possible, what is difficult, easy.... For it is impossible, utterly impossible, for the man who prays eagerly and invokes God ceaselessly ever to sin.
Source: Catechism of the Catholic Church (Vatican.va)