Who Hardens and Softens Hearts?

This evening, I was reminded of one of God's many capabilities. Exodus 11:3 says, among other things, that "the Lord gave the people favour in the sight of the Egyptians." That's something that God can do. While the Joseph Smith Translation makes it clear that the Lord didn't harden Pharaoh's heart, it's clear that He didn't soften his heart, either, which is also something He could have done. God can influence people's hearts. He just sometimes chooses not to.

I wonder how this fact of potential Celestial influence interacts with agency. Naturally, we are usually free to make our own choices, but what about when God softens hearts? I suppose it's possible that God's influence on our hearts is limited by our willingness to accept that influence. Then, could it not be said that the Egyptians softened their hearts towards the Hebrews, just as the Pharaoh hardened his?

I hold that each person is responsible for the hardness or softness of their own hearts, despite external influences. Sure, I get mad sometimes, and it can be difficult not to, but I can practice retaining control. People may irritate, and God can try to harden or soften hearts, but the choice is ultimately up to us. We choose what we so, and we, to a large extent, also choose how we feel. We can exercise control over our own feelings and emotions, regardless of the effects others have (or try to have) on us.