Habakkuk's book begins with a complaint that God is not listening and gets worse when God answers — the answer is that judgment is coming through a nation more brutal than the one being judged. Nothing in the book resolves in the prophet's favor. He does not get the outcome he asked for.
The ending is therefore remarkable. He lists everything failing at once: no blossom on the fig tree, no fruit on the vine, the olive crop failed, the fields yielding nothing, the flock cut off, no herd in the stalls. That is not a bad year. That is the collapse of every source of food and income a person in that world had.
Yet I will rejoice in the Lord, I will joy in the God of my salvation. The joy is not in what remains, because nothing remains. It is in a God who is still there after the inventory reaches zero.
The last line gives the image: he will make my feet like hinds' feet, and he will make me to walk upon mine high places. A deer moves confidently on ground that would break an ankle. Habakkuk is not promised flat terrain. He is promised the ability to walk the terrain he has been given.
He also admits, honestly, that his belly trembled and his lips quivered. The faith and the fear are in the same paragraph.