What should I do about my inability to lower my gaze from women in the marketplace, despite my repeated repentance and determination not to return to it?

You must fear Allah and lower your gaze from non-mahram women, for a glance is one of the arrows of Iblis, and it leads to fornication and regret. Remember Allah's gaze upon you when you fall into sin, and do not despair of repentance, for Allah forgives all sins. Allah Almighty says: "Say, 'O My servants who have transgressed against themselves [by sinning], do not despair of the mercy of Allah . Indeed, Allah forgives all sins. Indeed, it is He who is the Forgiving, the Merciful.' And return [in repentance] to your Lord and submit to Him before the punishment comes upon you; then you will not be helped. And follow the best of what was revealed to you from your Lord before the punishment comes upon you suddenly while you perceive not."