Much of the stress in our lives is brought on by the fact we are focusing on ourselves instead of on God. Trouble will find its way into each of our lives. Difficult, even tragic, circumstances will invade our serenity. Countless outside influences will cause us stress, but I maintain the primary culprit will always be a wrong focus. I know from personal experience that a surrendered heart that is thinking only of Jesus has no room for stress.
The love, joy, grace, and sufficiency of Christ have an almost intoxicating way of melting away every care and concern. Personal experience also informs me that even a slight glance away from our Lord yields disastrous results. The implication is clear. If you want to live a stress-free life, keep your focus on Jesus.