The definitions make sense in context of a task being easy to complete, or, in other words, natural for someone. But put in the context of my walk following Christ, these words are not synonymous. There is nothing about following Jesus that requires "little difficulty or discomfort." Jesus is frank about telling us that in this world we will have troubles. I never feel like I'm growing in faith when I am not disciplined in my thoughts, my effort, or my reflection. How can I be growing if I am not taking my thoughts captive to Christ, attempting to carve out a few minutes of my day for him, or meditating on Scripture? It's obvious that trying to follow Christ is not at all easy, much to my frustration. When I first became a believer, in many ways I assumed it would be. And maybe it was for the first couple months. But then it got hard--worth it, but definitely difficult.
Following Jesus is not easy, but it is natural.
We are made in the image of God. He formed each of us carefully and wonderfully with bits and pieces of his character within us. There are traits that aren't just "seemingly inborn," but in fact are actually inborn and cause us to desire God and be in relationship with him. We possess qualities and desires to follow God--or follow something--that aren't just happenstance or the easy thing to do. They are "implanted by nature," the nature of God.
So, although this may not be an epiphany for anyone else, it was for me. Though my walk with Christ will not ever be easy, it is natural. It's not something I have to force if I just remember that God created me to desire and worship him with my life. It is a natural thing. That's not to say I don't need discipline or effort, for the lack of those makes something easy. It means that, my character--the basic constitution of who I am--cries out for God. If I will only demolish the idea that this life, and following Jesus in it, should be easy, if only I will stop and be reminded of who God is and who I am, a relationship with Jesus might just come more naturally.