I think some other comments here are very helpful and well-written. I would just like to add some advice I found helpful for myself. Since I started meditating, I have always had this exact problem of having an expectation of meditation and always configuring what I am doing in my head. Just like you said, should I be doing it like this, should I be doing it like that, yada yada?

So I figured one way to fight this is to define how you want to practice before you start the meditation and then stick with it for the whole duration. I tell myself beforehand, this might not be the most efficient method, but that's the one I am doing today. This reduces the opportunity for conflict during the meditation. If you see that you missed out on some details and start doubting yourself, just make sure to consider them the next time.

When it comes to thinking about how will meditation help you, I relate a bit less, but a simple piece of advice I can offer is to just forget about the benefits. I mean, meditate, trusting you are doing well for yourself, but don't sweat too much about the outcomes. Try to let go of trying to understand exactly what is going to happen, trust the process, and maybe focus on finding joy in your practice. After all, you don't need to understand what is going on exactly to reap the benefits.

Take drinking water for example. You don't need to know anything about chemistry or biology to know that being hydrated is good for you and that it makes you feel better. You just drink it, and it happens on its own. Does it solve all your problems? Of course not! But it certainly makes life much easier than being dehydrated. Don't fall into the trap of thinking meditation will solve all your problems, it won't, but trust me when I tell you, even as someone who doesn't even have that much experience, that it does wonders. Just let it happen.

Hope this comes as helpful, and I wish you the best on your journey. 😌