How you live your life depends on what you believe. Some beliefs will help you find happiness, others will leave you feeling miserable. When you become attached to your beliefs, you might endure misery to protect your beliefs rather than challenge the beliefs to find happiness.
When you know that you are suffering, but you don’t know which belief is the cause, you can give up all of your beliefs and start fresh. If you know you are suffering, then that is the belief that remains. Believe that you are suffering. Next believe that you can do something about your suffering. Then start watching your thoughts. Your thoughts will suggest things to believe. Unless they support your happiness, don’t believe them. If they tell you you’re not good enough, don’t believe it. If they tell you you’re not smart enough, don’t believe it. If they tell you you’re not worthy, don’t believe it. If they tell you happiness is impossible, don’t believe it.
When you’re not feeling good about things, your thoughts may try to convince you of some awful things. When you get in the habit of suffering, your thoughts try to maintain that. By recognizing how your thoughts contribute to your suffering you can find some relief. Then you can find some happiness. Believe it.