Paul said that I may rejoice in the day of Christ.

Lutero said:
Paul said that I may rejoice in the day of Christ. He is not talking about losing his salvation. Everything with you is lose your salvation.

On the contrary, you can't lose something which you don't yet have. I am looking forward to my salvation with confidence in the mercy of God and the love of Christ. 

Everything with you is, "I save myself by my faith alone." With me it is, "I hope in God."

Sincerely,

De Maria