I wouldn’t sweat it. especially if it wasn’t intentional. Blasphemy is defamation of the name or character of God, which you didn’t do.
I just wouldn’t use the adjective “sacred.” Maybe blessed or joyous or personal. Divine Mercy brings the triumph and joy of Easter to the individual. Easter is the ultimate celebration of the Church, but DMS brings it home to me (and you, and each individual).
It might also be true to say that it’s the most important (or even sacred) to you. As long as you don’t try to speak in generalities (i.e. for the Church), I think you’d be fine. As baltobetsy says, it could be a good class discussion.