We are sorry to see you go, know that you are always welcome back!
In order to delete your user account:
Hover on your name at the bottom of the left side menu
Click on User settings
Click on Delete account and confirm
Keep in mind that if you delete your account as the only administrator, the whole company account will be deleted as well, along with all the data and other user accounts. If you want to keep the company account, make sure to give another user admin rights before deleting your own account.