Planning meals ahead of time

I have to do what I already know.  I have to plan my meals in advance.  It is urgent that I lose the weight and keep it off.  I lost over a pound today.  I am just shy under 300 lbs.  I wonder what my real goal is.  I would like to lose a lot of weight and feel much better.  Planning my meals is something that worries me as I can go over and eat more than what is allowed.  I feel like it is difficult to do so. However, planning my meals could go a long way into my losing weight.