This is such a confusing concept to me. I think it's totally unrealistic to expect that our wants will always align with what's right. I know that I should eat healthy. But sometimes I don't want to. The hassle with making the food, buying the food, spending time creating meals that are healthy but also tasty can be so stressful. If it's "empty" to do what's right when you're heart isn't in it, then what's the right thing to do here? If I don't eat healthy simply because I'm not fond of the hassle that comes with healthy eating, I'll gain weight and do harm to my body. Who cares if, initially, my heart isn't in it? The point is to start eating healthy. Once I did, I noticed myself losing inches without even exercising. I noticed an increase in energy, in mental function, in comprehension. I still hate the hassle that comes with healthy eating. But my heart is in it much more now than it was when I started because I see and feel the changes.
Point being, sometimes our hearts are not going to be in doing what we know to be right. As another example, sometimes my heart isn't into apologizing to my husband when I know I need to. Just yesterday there was a misunderstanding between us that I didn't want to let go of. I knew I should, and I knew I needed to apologize but I didn't want to at all. Yet, I still did. And after I did, I was able to let it go. My heart followed my actions.
I think it's naive to expect that our hearts will always be in what we know we should do. I think it can be healthy to do what we know is right even if we don't feel like it. In the example of the baby, I think it's understandable for the parents to not want to wake up every four hours to feed the baby. I think it would be wrong and selfish if they followed that want instead of being responsible, but I don't think it's realistic to expect that the love the parent has for the baby will always make them want or desire to get out of bed early in the morning.
Or another example, say a husband has a job painting houses. A man working that job here, where I live, would have to talk himself into getting out of bed in the morning. His heart doesn't have to be in it for him to get paid.
Spiritually, I believe our feelings and actions are equally important. However, I still don't think it's realistic to expect that our hearts will always be in the choices we know are right. Like I said about myself forgiving my husband, it took stepping forward in the action I knew to be right to get my heart to be in it.