My fault, my failure, is not in the passions I have, but in my lack of control of them.

The speaker distinguishes between having strong desires and being morally culpable for them. Passion itself is treated as natural—perhaps even vital—but the ethical failure lies in surrendering agency: letting impulses dictate actions rather than governing them. Read against Kerouac’s recurring preoccupation with appetite (for travel, sex, drink, spiritual intensity), the line frames self-critique in terms of discipline rather than repression. It suggests a classical, almost Stoic moral psychology: emotions are not the sin; the sin is being mastered by them. The quote’s force comes from its candor—an admission that the problem is not feeling too much, but failing to steer those feelings toward constructive ends.