Well, son, I'll tell you:
Life for me ain't been no crystal stair.
It's had tacks in it,
And splinters,
And boards torn up,
And places with no carpet on the floor—
Bare.
But all the time
I'se been a-climbin' on,
And reachin' landin's,
And turnin' corners,
And sometimes goin' in the dark
Where there ain't been no light.
So, boy, don't you turn back.
Don't you set down on the steps.
Cause you finds it's kinder hard.
Even though her life has not been the best, she keeps moving on and refuses to gives up (lines 8-11), even when perseverance seems like the worst idea (lines 12-13). 
 The image of life as a staircase implies a constant movement – for to get further on stairs, you must climb. The repetition of action verbs here – “climbin'”, “reachin'”, “turnin'”, “goin'”, etc. – further connects her actions to that of climbing a staircase, as well as characterizing her journey as one of constant movement. To participate in life, you must keep climbing – the movements of life  force you  to persevere.
Mother to Son