Tada Aoi - CANOE ~Nocturnal Waltz Remix~ [romaji and english subbed] 

it feels like every every single element beautifully connects to something else, and has a deeper meaning. i interpret this song as the journey that Tennouji went on in terra, and the fate of humanity

As long as humanity keeps moving forward, they will attain whatever goal they want, and it's okay if they loose everything in the process, as long as they keep moving forward. This connects with alot of elements of rewrite, the OP song "Rewrite" is about Tennouji, and shows us how he really is the most human in spirit, he keeps moving forward and when he comes to a stop he does not feel confortable. Humanity itself is in a standstill in rewrite, and tennouji is the one to get it moving again.