After being an active developer in the industry for about 5 years, I still have some bad dev habits on which I'm working on:
- Starting off with the code first without a proper design in mind/paper. (Trust me, I'll always regret of not having a proper design later)

- Writing long method bodies and not refactoring them later. (Because sometimes I turn out to be a lazy ass)

- Duplicating code in some places without reusing some.