An', Belllounds, you'll not last.

Unless you begin to control your temper, to forget yourself, to kill your wild impulses, to be kind, to learn what love is--you'll never last!...

In the very nature of things, one comin' after another like your fights with Moore, an' your scarin' of Pronto, an' your drinkin' at Kremmlin', an' just now your r'arin' at me--it's in the very nature of life that goin' on so you'll sooner or later meet with hell! You've got to change, Belllounds.

No half-way, spoiled-boy changin', but the straight right-about-face of a man!...

It means you must see you're no good an' have a change of heart.