One of the inherent problems with Catholicism/Arminianism is the ignoring of the eternal security provided by Christ's sacrifice.
Christ's sacrifice was complete on the cross; he died for His flock and paid the full price for your redemption.
But the Catholic/Arminian believes that Christ's work was not complete; that you are perpetually in jeopardy of losing God's grace. Thus the intervention of extraneous, self-serving church hierarchy is "necessary" to help you keep upright.
Calvin merely pointed out that if one is saved in God's plan, that salvation cannot be lost.
We live our lives according to His will; not ours.