The anxiety can contribute to difficulty in thinking, although physicians would not refer to it as "playing tricks on your mind." In reality, the human brain can become easily distracted, so that you make such a mistake in returning home, and feelings of anxiety can do this.
Yes, over time, persons can get to the point that the medicines for anxiety will no longer provide the benefit that it once did. It is not usually a problem that a medicine will build an excess once stabilized on a dose, unless there is a change in the body's metabolism. For example, if a condition were to develop that would affect the liver metabolism of a drug that someone has been taking for years, the level may rise to an excessive level.