But how can you be certain what is in your control?

Someone will say: ‘But even my thinking is not in my control entirely, externals influence it…’ Agreed, many external things influence your behavior like, the way your parents raised you, or the culture around you, and so on; but as soon as you understand that you have the power to influence and alter your deep beliefs, the power comes to you. Call it mental programming, subconscious patterns you can change it. It might be hard, but it’s not impossible. And would you rather remain in the miserable state or over.