Your baby may fight sleep because they don't want you to leave. It's likely that they're feeling some separation anxiety, which can show up at bedtime as well. Often seen anywhere from 8 to 18 months. So, you can reassure them it is okay to rest. Be compassionate yet firm in your tone. Place your baby in a dark room. Change their diaper. Swaddle them, if they are still young enough to do so.