Reading are here.
John of the Cross at Wikipedia and John of the Cross at New Advent. This John is not the same John that was with Jesus, but a man much later in time (1542-1591). I link to both because Wikipedia gives an easy to read summary, and New Advent is much more thorough but harder to read.
And yes, I am aware I don't do this on all the different days of the year. Yesterday was the Memorial of Saint Lucy. Some days I do, some days I don't!