It enlightens the soul

You gain two graces when your strive on the side of God. One is the comfort of the Holy Spirit, which fills the soul with joy, peace, delight and so forth. The other grace is what we call the experience of temptations. This grace of experience is indelible in the soul, in other words it never leaves us, because it’s united to the heart which was subjected to the experience of the temptations. The first grace, that of the Holy Spirit, sometimes comes and sometimes goes. At times of temptation, the second grace, that of experience, is more useful because it illumines the soul as to how to get through the temptations, since it has experience of them and so already knows how to free the soul of them.