So confused with net calories?

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Ok, so my understanding that the ideal calorie intake to lose weight for a woman is 1200 calories, but what I don't understand is that before or after exercise? Like should I eat 1200 calories, then burn say 500 leaving me with a net of 700 calories, OR should I eat 1700 then burn 500, leaving me with a net of 1200?

I'm trying to make a healthier lifestyle change. The thing is, I LOVE food. Though I've made the change to eating nutritious (and I feel great about it!) with lots of fruits and veg and non processed junk, I still eat a lot, and the food I eat is higher calorie, I guess because it's more nutritionally dense. (I.e. white vs whole wheat). For this reason I find it near impossible to achieve 1200 calories. Yesterday I ate around 1600 calories but burned around 400, so I was good. Today, however, I ate about 1950 (sigh) and burned around 500 (net of ~1500). Will I be able to lose weight this way?

I'm just feeling really down on myself because I feel like I just can't meet these expectations that everyone says I need to make to lose weight, let alone sustain them in the long run. It's hard. I'm between 5'6 and 5'7 and 165lbs, by the way. Thanks for any advice, and I apologize for all that ramble.