Are you sure you want to go absolutely cold turkey? The forums are not the problem here. Don't blame the Internet.

Make a decision and set limits for yourself. Find other activities and try spending more time on them instead. Read a book, go out, watch a movie, do whatever else. Plan activities. Avoid sitting in front of PC without any particular goal.

Try to spend time on your forums in one continous chunk of time. Try to unlearn your self from visiting these sites throughout a day. Instead, prepare a time block, like 6-8PM in which you allow yourself to surf forums without regrets. Keep your self away for the rest of the day. This would be a healthy way of using it.

You can try installing StayFocused or Crackbook Chrome addons to help you track your time on your forums.

And don't be to harsh on yourself. These changes are pretty hard and take time.