The Purpose
In the last scenes I kept asking myself why did he loop it. Why did he choose to feed the loop, instead of breaking it, if he had suffered so much.
It's explained in the movie. It's the purpose. He had the choice all the time, and chose to keep doing it. He suffered a lot, yes, but it was only that way that he'd be able to meet himself, and fall in love by himself, and meet again himself.
It's the idea that it's better to suffer but meet the person you loved, than never meet her.
Once the main loop ends, his new purpose and to create the agency and make it grow, so that the whole thing could be possible.