Your mind is a very complicated entity. It has been suggested that looking at it as a network (or an ecology) of multiple agents is a more useful view than thinking about it as something monolithic.

In particular, your reasoning consciousness is very much not the only agent in your mind and is not the only controller. An early example of such analysis is Freud's distinction between the id, the ego, and the superego.

Usually, though, your conscious self has sufficient control in day-to-day activities. This control breaks down, for example, under severe emotional stress. Or it can be subverted (cf. problems with maintaining diets). The point is that it's not absolute and you can have more of it or less of it. People with less are often described as having "poor impulse control" but that's not the only mode. Addiction would be another example.

So what I mean here is that the part of your mind that you think of as "I", the one that does conscious reasoning, will have less control over yourself.