There were many reasons Thor crossed a galaxy or two in order to return to one Jane Foster. Mostly, it was because Jane Foster was everything he wasn't, in a way that made him love her. Of course, Loki, Darcy, and even Tony Stark were the complete opposite of him. But they were different from Jane as well.
Where Thor was still a bit brash, slow on the uptake, and used brute force, Jane was calculating, on top of things, and gentle. She was improbably intelligent, accepting, and kind. She had taken him in when he returned and forgave him for what he had to do. She was not upset, merely overjoyed that he had come back to her. No word of broken promises was spoken; he had kept the promise, though it was belated. The two were nauseatingly happy together.
Perhaps his favorite thing about her was her gentleness. Raised amongst warriors and kingsmen, it was not a trait he often found.
Even if she was frustrated and tired, she was never anything but soft towards him. Jane was kind even to Leo, the cat that still had not taken a liking to her. (Which Thor could not grasp; he didn't understand how a creature could not realize her worth.) She was harsh towards those who angered her - as he had seen once - but only within good reason.
A fine example of her gentleness occurred on the very day Thor thought all of this. He and Steve Rogers were sent on a mild mission to take down a few anti-mutant protestors that happened to get their hands on threatening weapons. This small take-down had not tired Thor in the least, but it was one of a constant string of small things Director Fury had ordered the Avengers to do. He voice his dislike of this. Not only did Jane sympathize, she offered to make him feel better.
He did not understand why Darcy snorted into her coffee (a drink much too glorious to snort into) and fled the room in laughter. Jane scowled at her retreating form before moving to stand behind Thor.
Her hands, pale and rather firm, rested on his shoulders for a few seconds. Then her fingers were working their way onto, around, and against the sorest spots of his shoulders and neck. The god of thunder had never felt something so lovely. Jane "massaged" (which he thought to be an odd word) his shoulders for an undetermined amount of time, as he fell asleep.
Looking at the softly snoring man, Jane smiled. She spread a throw blanket across him, turned off the light, and read by a low lamp for a while. He had been working hard to better a world that wasn't his own. Fury put a lot of stress and even more work on the team, and it was getting to Thor.
When his phone rang at half past midnight, she turned it off. If it was an emergency, they would call her to get in touch with him.
Otherwise, Jane Foster thought her demi-god deserved a night off.