I just got a tip this week from another magnesium oil fan. It seems that magnesium oil can work "locally" wherever you put it. This may explain your overactive mind.
Try using the magnesium oil on your feet, legs, or body, but avoid your upper body, especially your neck and head. Applying it on your lower body will allow the magnesium to absorb transdermally, but not to "go to your head." You might try using the oil just on your feet, or taking a 20-30 minute footbath. If this technique works for you, then you'll know that full-body baths can stimulate your mind or energize your thoughts.
As further evidence of a local effect, I have several friends who spray the oil on their head, face, and neck because it improves their memory. This definitely suggests a powerful local effect. Because magnesium chloride is absorbed transdermally at the site of application, it seems likely that body tissues nearest the application site gain the most benefits (or the greatest effects, as the case may be).