I have had this issue with my cats, Cassidy and Delaney, in the past as well and I think it's an important question since so many cat owners (new or otherwise) struggle with finicky, picky eaters. And it can be so frustrating when our furry loved ones refuse to eat when we know that they need to in order to remain healthy and happy. But, luckily, this situation is a one that is easily fixable -- at least that has been the case for me and my girls.
Before I adopted Delaney, I had just Cass and she ate only half of a 3 ounce can of wet cat food. Therefore, I was keeping the other half of the can in the fridge to use the next day. And I quickly found that while she'd willingly eat the first half of the can, she would turn her nose up at the same food the next night. And, let me tell you, it drove me insane because I couldn't figure out why she was acting so finicky about her food. Because she had lost some weight due to her odd eating patterns I had taken her to the vet to see if they had any insight and they were the ones that caught the fact that she was most likely not as interested in the canned wet food the second night because it was chilled whereas the food was room temperature the first night and therefore more palatable. And it wasn't just the fact that it was cold on her tongue, either. The chilled food tends not to have as strong a smell as the food when it is room temperature or warmer and since cats are drawn to food by its scent, Cassidy wasn't as interested in the food when she couldn't smell it as well. So the vet offered up a couple of different options: (1) use warm water or warmed chicken broth (low sodium, all natural) added to the canned cat food for the second serving -- not only will it add warmth, but it will make it seem "fresher" too, (2) take the canned food out from the fridge about an hour before serving so that it can take the chill out of it, (3) put the contents of the canned food into a microwave safe dish and then heat for 5-10 seconds or until warm (but be careful that it doesn't become hot as microwaves tend to heat unevenly), (4) heat the can on the stove under medium heat -- this is also useful if you add fresh ingredients to your cat's food (again, use caution here as it is possible to overheat the food), and, finally (5) try to encourage your cat to eat an entire 3 ounce can of wet food at once (this is only appropriate in some situations).
Now that I have Delaney and both my girls are still growing, I am feeding them each an entire 3 ounce can of wet food each evening. Therefore, this isn't so much of an issue for me anymore. But, trust me, I feel your pain -- feeding cats can be difficult and frustrating at times. But rest assured that you're on the right path and that, at least, for this particular scenario, there are a lot of options and possibilities out there that can help both you and Cammy take care of business