Aside from being atheist, you surely don't think of God every time you win because you are in your comfortable state. You think nothing but to enjoy since everything is all under your control. On the other hand, pious people out there definitely thank a lot in God for how blessed they are every time they meet their goals but since you are not one of them then for sure you only rely on your capabilities claiming that you are the superior of your own. But when losing streak comes, there's a point that you now feel frustrated, confused and can't explain what's the reason for those miserable events which later result to calling God. Your mind and body tend to call Him because you are already hopless and feel helplessr right that moment. You treat God as your last resort for solving such problems.
Anyway, don't worry mate, that is normal and expected from an imperfect individual like you (us) For sure that most of us think the same way