custom更多指风俗人情
It's a custom to get togehter on X-mas Eve.
habit指个人习惯
We should't fall into bad habbits.
hobby业余爱好
My hobby is keeping animals.
habit个人习惯
custom特定地区人们的风俗
hobby个人爱好
Working at night is not a good habit.
You better not do that. The custom here does'nt allow that.
Collecting stamps is one of my hobbies.