Practical psychology hasn't changed much. For the past 100 years, it has required the presence of a trained professional; but that time is now past. Earlier it would have been entirely unthinkable that anyone could treat themselves for psychological discomfort, for hard-wired feelings like jealously, for phobias or bad habits. But think about it for a moment. It's not the treatment professional who has the problem, it's you. And that professional needs to use time to understand your problem and then figure out a treatment process that can help you. That can be expensive and time-consuming. What if you could solve the problem yourself while you relaxed, and when you had time? Your subconscious contains both the problem and the answer to the problem. But what is the subconscious?
The subconscious always wins
Right now as you read this, you are both conscious and unconscious at the same time. In other words, you have some learned reflexes in your subconscious that help you read words and understand them. Your conscious mind can then reflect on what the words mean. Your subconscious registers everything that goes on before your consciousness registers it. That means that your consciousness is in many ways a slave to the learning hidden in your subconscious.
In your subconscious lies everything you have learned automatically. Not just practical knowledge, like how to ride a bicycle, how to read, or how to brush your teeth. There is also automatic emotional knowledge. This automatic emotional knowledge can be pleasant feelings or what some might call "dumb" feelings that don't help you. They can be released automatically and are outside the control of your willpower. But where do they come from, these "dumb" feelings? And why don't they disappear by themselves? They don't disappear because at some point in your life, your subconscious learned that they were significant and something that it was important to keep an eye on. The subconscious received knowledge, but also a bit of a shock, which its trying protect from you going forward.
Do it yourself
These feelings are within you, and they come from you. Your actions come from within you: nobody else is controlling what you do or experience. It's not your surroundings or other people who are creating these feelings in you. It's you. It's just not your conscious mind. It's a part of you that you don't know about. Your subconscious learned something at one point and is now trying to help you away from something or towards something the only way it knows: to create feelings within you. Both pleasant and unpleasant feelings can get you to do the wrong thing. The good news is that it's you yourself doing it, which means that it's you that can change it. All you need to do is work with the problem in the right place.
TIP: Solve your biggest problem first. That's easiest and will give you the most satisfaction.