I don't know about you, but when I walk in the kitchen hungry, I eat the first thing I see. That is why, I try to stock my kitchen with healthy snacks. I keep keep things like fruit (fresh and dried), nuts, yogurt, veggies, multigrain crackers or chips, and cheese in easy reach.
I like to to prep and freeze basic ingredients I use for multiple recipes. If I am chopping onions, celery, carrots for soup or a stir fry, I chop much more than I need and freeze the extra. Same thing when cooking meat, soup stock, rice, quinoa, or couscous. I freeze the excess.
The one thing I don't freeze but prep in advance is salad greens. I love my salad spinner. I find even bagged greens last much longer if they are all rinsed once the bag is open, and the bad leafs are removed. I drain the excess water out of the bottom of the spinner and I keep the greens in the spinner, storing them in the refrigerator using them as desired for around 1 week. Another tip for making great salads is to keep a variety of nuts, seeds, and crumbled cheeses in the freezer.
It makes it much easier to make a healthy meal, when most of the prep is already done. It is like being my own Sous Chef.