Do we purposely derail our own self-regulation? 

Alcohol is consumed, to excess, even though we know that it will lead to risky behaviors, bad choices, and regretted nights.

Homework is put off, though work will decrease, because it can be completed faster under pressure. 

Relationships fall apart because of lack of fidelity, though there is no way to cheat except for conscious action.

The theories of self-regulation as strength, as a coping mechanism, in any sort of scientific sense, are in my opinion ultimately subject to the idea of personal will.