This is the Aristotelian teleological causation. A goal generates a behaviour. Finally, the distinction between reasons and causes is not sufficiently developed to really tell apart teleological from scientific explanations. Both are relations between phenomena ordained in such a way so that other parts of the world are effected by them. There is a myriad of answers to these questions.
Mental causation is a foggy subject, to put it mildly.
Perhaps the only safe thing to say would be that cause and goal need not be confused. A person can act to achieve some future thing but it is not a future cause that generates his actions as an effect. The immediate causes absolutely precede them. The contents of mental imagery are not subject to the laws of physics and to the asymmetry of time. The physical world and its temporal causal order are.