You can feel yourself climbing: forgetting what's behind you and straining toward what's ahead.
When you sense yourself climbing higher in how you live, so that you can say with Paul, "forgetting what is behind and straining toward what is ahead", you have the fifteen Songs of Ascents to say at every step forward.
Letter to Marcellinus
He gave all fifteen Songs of Ascents for this, Psalms 120 to 134.