To me this could be interpreted as a deeply spiritual song. Well the first lines in fact start off expressing the nature of duality ("within" and "without"), yet as Spirit ("freedom") permeates absolutely everything in existence, it can be found in both the inner and outer worlds.
Many battles in the game of life as we strive to improve, to find meaning, to find God (or whatever form of Spirit you resonate with). And yet, again because Spirit is everything, Spirit is with you always, and eternal... so "you'll never see the end of the road / While you're travelling with me."
Like others have said, yes the song is in the obvious sense, about not giving up. "World" ("when the world comes in") references the physical/material aspects of life, which is delusion because literally nothing is actually solid as we understand it (all is vibrating energy, and this has been scientifically proven since a few decades ago). So the physical world/delusion of duality is constantly "coming in" (to our consciousness/awareness/mind) to separate Spirit and soul, to make us forget the truth that we are individualized pieces of Spirit.
"My possessions are causing me suspicion / But there's no proof"--the fact again that all the troubles we find in the physical world is in fact not True, yet as we have not yet achieved God-realization, we do not have capacity to find "proof" of the unreality of our material possessions. The car that is being towed could be symbolic of our human body-vehicles. We have "suspicion" because as souls, we DO have an intuitional knowing, it's only that temporarily we may not have conscious awareness. Intuition by definition is an understanding of Truth that may not (often does not) necessarily have physical evidence.
"Now I'm walking again / To the beat of a drum / And I'm counting the steps to the door of your heart"
Now that the perspective that is being represented by this song has come to the point of some type of awareness of Spirit, he/she is now returning to God's heart, or Love which is the only and true Reality. Heart is significant because God watches your heart above all, He is all about Love, is Love itself.