Objectively, how do you know that whenever you feel the feeling of pain, that means "do not do that". I get that from an evolutionary point of view, it makes sense, but how do YOU know that is how you're supposed to act when you feel THAT feeling. Did your gene call you on the phone, and told you "listen, when I give you this signal, it's called pain, and that means stop doing what you're doing". If you are in control of your behaviour and your behaviour is controlled by your thoughts, and not your emotions, then at some point you would have had to make the decision to actually "let's avoid pain". Since you never made that decision, it's the pain emotion deciding it for you, not YOU or your thoughts. So YOU do not know why you're doing what you're doing, you need to ask your emotions, and you have no clue where they come from.
Now you could argue for evolution in that the emotions come from outside of YOU, in particular they come from the universe, because it is how the universe tells you that given its physical laws, if you act in a certain way, you will not exist, and you can only exist if you act some other way. But as we established, these are outside of you, so you're sitting there clueless and watching "you doing things without knowing why". Also, you can wonder about why the physical laws are like that, no idea about that either...
So If I get this right, I have control over my beliefs, so I can change them to desire whatever I want through my thought. So first question, how do I decide what I should believe and what I should desire. Is it arbitrary? Do I flip a coin? I think the problem with this train of thought is that it's putting the cart before the horse. The first step in shaping my belief is that I want to change it somehow, I already have a desired end state. Now that first desire is handed to me, from who knows where. Probably from evolution, universe, God, etc... but it's definitely coming from outside of me and directly telling me what to do without me knowing why.
But let's assume that I can change my beliefs. So how should I change them? Could I say believe that putting my hand in fire is the best thing ever? Could I believe that there's a door in that brick wall and I just go through it repeatedly (by banging my head). Could I believe that I do not need food? I might have the willpower to do all of these for some time, but unless I'm getting a hit of dopamine, I will give up eventually. Finally, could I believe that I should kill myself and that's 'desirable'? Or whatever I'm doing now, is the 'desirable' thing to do. I guess if all these were true, then people (and things) could believe or desire anything and the world would be total random chaos. Since there is some order, and laws of universe, and evolution, this is not the case.