This is actually correct, thus, we are advised to sleep when the baby sleeps. But I know in your case, it'll be hard because you spend the day working. I understand that it can be frustrating. But I guess that your frustration comes from not sleeping at night. Take a nap during office breaks so that you'll have enough energy to go through the night. your baby's sleeping habit and schedule will change in no time. so for now, just bear with it.