(1) custom 指传统风俗、习俗，也可指生活习惯，后接不定式。
They broke some of the old customs.
It is the custom in China to eat dumplings during the spring Festival.
(2) habit 指个人生活习惯。“(有)养成……习惯”常用
be in / fall into / get into / form / have the habit of doing sth.
give up / kick / break away from / get out of the habit of doing sth. 句型。
It's easy to get into a bad habit but its hard to give it up.
The drug easily get one into the habit of smoking.