You need not think but a spirit will make you think at any occasion. During your lifetime you are living with many spirits. Some of them are representatives of the people you met in your life. It is one of the natural qualities of spirits.
Spirits are separate elements. A human being is not a single spirit. A human being during his/her life time is living with many spirits which have joined one by one since birth. They are knowledge, skills, feelings, emotions, interests and everything. Even thoughts are not your own. For example, when you want to take a decision on a subject, one after another the spirits think and you just listen, choose or reject the ideas which they transmit to your mind through your brain in the form of thoughts. A human being is just a robot made of flesh and bones and a toy of the spirits for their games.