Cognitive Behavioural Therapy has come to be known as a gold standard treatment for many mental health problems, from anxiety and depression to addictions, obsessive-compulsive disorder, addictions, and more.
The Society of Clinical Psychology of the American Psychological Association lists Strong Research Support for CBT as a treatment of many disorders.  

Psychotherapy began with a strong focus on psychoanalysis (most commonly associated with Freud.) This involved the traditional idea of the client laying on a couch with an analyst listening quietly and exploring
the unconscious, hidden desires, repressions and defense mechanisms. 

Dr. Aaron Beck was trained in psychoanalysis but he began to find patterns and connections in how clients were discussing their symptoms of anxiety and depression. He identified that low mood/depression was associated with pessimistic
thoughts, and anxiety with a bias on thoughts preoccupied with worry or a sense of impending doom.

He said that because everyone reacts differently to different situations, the situation itself must not trigger the emotion, there must be a thought within that. My analyzing the common problematic thought patterns (also
called cognitive distortions) one can begin to change their self-talk, and their thoughts can begin to resemble the way they might talk to a friend rather than the critic that many report their internal monologue becomes. 

These are just a few of the tools commonly used in Cognitive-Behavioural Therapy

Thought Records

Thought records track the connection between a situation, one’s thoughts and one’s feelings along with the physical sensations and behaviours that follow.

Evidence Technique

After doing a thought record, the next step is to analyze the evidence for and against the thought. By writing this out, it leads one to consider whether their thoughts are in balance or whether they might need to be re-evaluated.

Tracking: BAI & BDI

The Beck Anxiety Inventory and Beck Depression Inventory offer a score based on how often clients experience common anxiety and depression symptoms, it can then be tracked on a graph which allows one to see trends in mood and evaluate
changes over a specific period. 

Once one identifies their thoughts and connects them to the emotions associated, they can drill down a bit further until they connect to the client’s specific core beliefs (also called schemas). These are like people’s
framework for understanding the world or big-picture beliefs about things like how lovable they think they are, how safe, the world is, what people are like, etc. – usually these beliefs are acquired in childhood and oftentimes they
become deeply instilled and can become very difficult to change. Understanding the underlying patterns of schemas can help identify the beliefs that have led to clients’ long-term problems of thought, emotion and behaviour.