A key to critical thinking is realizing "you" are not in as control as you think you are. I am not referring to "free will" or other metaphysical concepts here; I am referring to overwhelming evidence of the biological drives, cognitive pressures, and social/environmental situations that guide our beliefs, thoughts, and behavior.
Perhaps the most universally experienced and least controversial example of this concept is our physiological needs linked to individual survival such as eating, sleeping, and excreting wastes. We can only control our behaviors for so long until biology takes over. Before we get to this point, most people "decide" to make dinner, "decide" to go to bed, or "decide" to excuse themselves and find a restroom. These are all virtually undisputed examples of how our physiology greatly influences our behavior. What about situations?
In July of 1961, Stanley Milgram began a series of experiments showing how ordinary people can do monstrous things (administer painful and even lethal shocks to innocent victims) simply by putting them in a carefully crafted situation. In the Summer of 1971, Philip Zimbardo created a mock prison environment situation which turned a group of Stanford college students into sadistic torturers. Since then, thousands of similar (but less ethically questionable) studies have been done demonstrating the power of the situation to change a person's behavior, beliefs, and in some cases, disposition.
What does this have to do with critical thinking? We can only begin to understand our own beliefs and behaviors when we stop attributing everything to some metaphysical "self" and start understanding the circumstances that lead us to form beliefs and behave the way we do, and this kind of self understanding will inevitably lead to greater understanding of others.