I had posted previously on what I put as the number one Rule of Weight Loss: Make the Decision.
I honestly believe (partly from what I've read from studies and blogs and partly from observation) that a lot of people lose track of what they eat and, more basically, have no idea just HOW much they are eating in terms of calories.
I've seen assorted systems. Exchanges (so many meat, so many starch, so many veggies) and Points (Weight Watchers) and Plate Portioning (half simple veggies, a quarter lean protein, a quarter complex starch) and the standby old-fashioned calorie-counting. I've seen successful losers do a countdown (a simple notepad they carry with allowed calories or points on top and then a countdown as they eat, subtracting to 0, then stop eating). Some do electronic tracking (on a smartphone, online, on some gadget). Some have nice journals. Some have great memories and just add it up in their heads as mouthfuls are consumed.
However you do it that is accurate enough to work for you, keep track of what you eat. Learn what makes for a weight loss or, if you are at goal weight, maintenance level of food (by points, by calorie, by plate configurations). Make sure you get your calcium, protein,, fiber, and nutrients by eating variety and taking good supplements on days when you fall short.
Eventually, you'll habituate to what is a proper portion/ratio/quantity.
So, yeah. Keeping track of food intake. Studies* have shown it helps dieters. Awareness, no fudging, no lying. Knowing what is going in. It's important to learn how much should go in....
* Too lazy to look em up. You have a search engine. Use it. :)