I believe that God made the whole of us, so that if we are engaging only part of our being in our faith journey, then we are missing the whole of the Gifts that God has given us, although each person's gifts will be a bit different.
The problem with too much emphasis on the feelings (so called-heart knowledge) is that when we have down times, we might think we've strayed from being saved, i.e. we don't "feel" saved. And the bigger problem with that, from a Lutheran point of view, is that we put the emphasis on what we have "done" or "felt" or a "decision we've made" rather than on what Jesus accomplished 2000 years ago.
The problem with too much emphasis on the confessional type of faith, perhaps "head knowledge," is when it doesn't move beyond that. At its worst, it is saying we are saved because we say we're saved just because we say the creed on Sundays. At its best, a Confessional faith carries us through the down times of blah feelings of our faith because we Know (head knowledge based on the Bible) we are saved because of what Jesus did 2000 years ago.
I learned this last point in a very real way during a difficult time in my life. I couldn't pray or truly participate in worship, but I learned that the Holy Spirit truly did dwell in me since the time of my baptism, just as I had been taught in the Lutheran Church. I was "still saved" even though I wasn't able to put anything "into" this faith at that time.
Jesus did the work...so what is our response? That is where others will see what this means to us. Are we grateful? Joyous? Serving others? Maybe these are the things that really make a difference between the head and heart knowledge. This Lutheran message is a big deal. Do we act like it is a big deal? Not that these actions save us.
On the other hand, if we've come to faith because of hearing some preaching of the "feelings" of faith, that is still real faith, because faith comes from God. And the Lutheran confessional way can help people like this who have down times.
Luther encouraged a daily decision to live in our baptismal covenant. These are the thoughts, actions, prayers and feelings that we have based on our response to the Gospel message. One of my favorite verses is 1 Peter 3:15. It implies that there is outward evidence, perhaps joy, of the "hope that you have." It goes on to mention "good behavior in Christ."
I hope this clarifies my "feelings" and "thoughts" on my faith. I think the verse from 1 Peter shows that somehow we tell others by the way that we live it out, not by theology.
Discussion prompted by God’s Upside Down Kingdom at http://frombelow.wordpress.com/