This prayer is absolutely beautiful, I found it in a small book called ‘The Pieta Prayer Book’ that you can buy on the internet. People believe this prayer was said fiftieth years of Our Lord, Jesus Christ. I have said it off an on for years and it gives you a greater appreciation of Saint Joseph and a warm love for Jesus. According to oral tradition, people who basically pray it or hear it read will not die of a sudden death, drowned, poison won’t take an effort, or be burned in any fire, or will fall into the hands of their enemies or be defeated in battle. I think you really have to pray this prayer daily for all these promises to be fulfilled. Having the Statue of the Sacred Heart of Jesus for example have very beautiful promise for those who honour it in their homes. The things is people will get the statue and totally ignore it and then expect protection, that is not what God means, the statue is suppose to remind you every time you look at it to think of Jesus’ love for you and so many people do not but expect all the favours God promises as if they do.
So I believe this prayer is meant to be said daily really if you want all that it promises to happen. It is said if you say this prayer every day for nine days, your prayer will be answered. Once again it is common sense to realise if the prayer answered is going be harmful to you in the long run it won’t be answered. Saint Joseph knows the prayers that please God and the ones that will give Him glory.
The Prayer of Saint Joseph 
O St. Joseph, whose protection is so great, so strong, so prompt before the throne of God, I place in you all my interest and desires……..(make your request here)…..
O St. Joseph, do assist me by your powerful intercession and obtain for me from your Divine Son all spiritual blessings through Jesus Christ, Our Lord; so that having engaged here below your heavenly power, I may offer my thanksgiving and homage to the most loving of Fathers. O St. Joseph, I never weary contemplating you and Jesus asleep in your arms. I dare not approach while He reposes near your heart. Press Him in my name and kiss His fine Head for me, and ask Him to return the kiss when I draw my dying breath. St. Joseph, patron of departing souls, pray for me. Amen.
The last bit would of have been added on at a later date, I would say, regarding to Saint Joseph being the patron saints of departing souls.