Custom
Habit
noun, の adjective
I've learned to be accustomed to this. It has become my custom and habit.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
「たばこ、止めたんじゃなかったの？」「まあ、ほら、『古い習慣はなかなかなくならない』って言うだろ。」
"I thought you quit smoking." "Well, they say old habits die hard."