Lena, have you checked out the frozen aisle at Walmart? They sell a giant bag of stirfry vegetables that you can prepare last minute. It's a resealable bag so you can make as much or as little as you need. I always buy several of those because they are great for you and can be prepared in no time. I also love canned green beans. Did you know you can eat an entire can of green beans for around 100 calories?
One of my other staples is the extra large bag of frozen chicken breasts. Sometimes I cook them in a pan with a little bit of olive oil, other times I bake them or throw them on my George Foreman grill. Very versatile. I also really really like the stuffed salmon from Sam's Club. I usually buy a couple of cases, split it up into 3 or 4 piece packs & freeze it. Takes less than 30 minutes to bake it in my little convention toaster oven. I keep a lot of canned tuna on hand, too. Very versatile. Great on top of a salad.
Soup... I always have a big pot of homemade soup in the refrigerator. Soup is great for you and endless choices as far as varieties.
The key for me on healthy eating is maintaining supplies that offer a variety of good choices & always shopping for things that can be prepared quickly.
Of course, healthy eating is only half of the equation. I try to exercise on a daily basis and since I find going to the gym to be such a pain in the butt schedule-wise, I keep a stairmaster at home. Half the time I do it in my pajamas. You can find a lot of really great used exercise equipment on craigslist or the Facebook yard sales. I bough a real stairmaster for $75 and they even delivered it.