Billbo got accustomed to the way he lived his life. He had his routine, his garden, his pantry and respect of Hobbit's community. No one even considered him a real Took anymore.
He knew how to avoid things he did not desire near his home, and also how to get those small pleasures in life. Younger days, when he dwell upon lack of any deeper and meaningful connection to others, were behind him. He found his relations satisfying, he couldn't get too much out of his relations, but again he didn't get really hurt. It was comfortable life and it was quite enough for him.
You could say that he was proud of his small life he adjusted everything to match his taste and inclinations. Right books and maps came his way. Even his chairs were placed on perfect places where everything would be in arm's reach.
That's how trouble found him. He got confident in his life and place in the world. He saw no reason to look beyond borders of Shire. He had red enough books to know for sure that there is only sorrow and danger out there, especially for little folks like he was.
He was bathing his face in the sun, enjoying his pipe he always got in the afternoon. He didn't even have to look at perfect circles he was making in front of his face. Then suddenly the perfect moment was ruined as the smoke somehow found a way back to his mouth. As he coughed he opened his eyes and squinted on the bright light. He could see he wasn't alone anymore. Tall dark figure has stared at him making no effort to cover up his rudeness.