It is also ok to indulge occasionally.
It's good to eat healthy substitutes of what you're craving because most of the time cravings are the bodies way of saying you need something. Instead of a fast food burger make a lean burger at home. You may be craving the iron in it. And try eating sweet fruit to hold back the sweets craving. The sugar in fruit is easier to breakdown :)
It's not bad to ignore unhealthy food cravings. You don't want to load up on fast food all the time. I'm not one to talk though lol because this pregnancy I've definitely overindulged in unhealthy foods. I've had a lot of milk duds and ice cream and sausage mcmuffins. Fortunately I've only gained 9 lbs so far and I'm 30 weeks and 3 days lol, I don't how my body's managed that.