Your belief-system is what causes you to think and feel the way you do. Your belief-system will determine whether you're depressed, happy, sad, excited, or bored.
Your belief-system determines your courage, fears and behaviours.
You only need to examine your life to see your belief-system at work, as reflected in your level of success, your health, wellbeing and the quality of your relationships.
Your belief-system is your "auto-pilot" — the beliefs you hold and the "facts" you automatically take for granted. Your auto-pilot makes you do what you do, and is the root source of all the wonderful things in your life: the loves, the fun, the money and the pleasant surprises, as well as all the drama, conflict, frustration, stress and other negative situations.
An unknown author wrote (the following is, I believe, incorrectly attributed to Viktor Frankl):
"Between stimulus and response there is a space. In that space is our power to choose our response."
In other words, between something happening to us, and our reaction to that event, comment or action, we pass, albeit often quickly and without much awareness, through our belief-system.
Understanding and learning to "catch ourselves" when responding in habitual ways is a key to change. We learn that we are not victims to emotions, and that we cannot justifiably blame drugs, alcohol or other factors such as culture or peer groups, for our behaviours. Most importantly we learn we are not "victims" to some difficult-to-reach subconscious — it's all available to us consciously if we remember to catch ourselves responding habitually, particularly those responses and emotions that we fear, or wish to avoid.,,