inveterate

A person who is habitually engaged in a particular activity, often something undesirable, and is unlikely to change their behavior; for example, a liar or a gambler.

老毛病（指很难改掉的坏习惯）

• He's an inveterate smoker; he feels unwell if he doesn't smoke for a day.

他是个老烟枪，如果一天不抽烟就会觉得不舒服。