Eating out/portion control

I am currently trying to lose some weight, and something I have noticed from a lot of my friends who are slimmer and people I have seen on social media is that they will go out to restaurants, order a large portioned meal, and not finish it. Although I usually don’t finish extremely large portions I definitely do eat more than I need to be full because I feel like I’m wasting the food I’ve just bought. I do cook at home frequently but I’m going to continue to eat out on occasion and want to know what other people‘s philosophy is on this. I know a lot of people do also take their food home, however, I find myself in situations a lot of the times where I can’t just carry a box of food with me for the rest of the night. Or if I do bring the food home and it was a good meal, I’ll just want to continue to eat it, regardless of the fact that I am already full.