The gateway for all your responsible gambling needs is the “Personal Limits” section, which can be found within your account profile. From there, you can set up limits to prevent you from gambling beyond your personal limits.
You can tweak the settings for max bets, losses, sessions, and deposits from this page.
For more serious limits, you will have to contact Customer Support through email to enroll. The options here include cool-off periods and self-exclusion.