It's pretty easy for me to tell at this point what it's like when I get "hooked." Ruminating has always been something that I do actively rather than with half of a mind. I actually suffer symptoms that feel like withdrawal symptoms when I neglect to ruminate -- dark pits in the soul, I'd call them. I also get a powerful fear that I'll be losing out on precious insight into situations, despite the fact that I usually do just fine in life without all this "extra" insight. I typically know what I want to do when I need to.
I do know that the brain is very malleable. This will take work, but it's something that I want to keep up for the rest of my life. Believe me, if it's made this much of a difference already, who knows what the future will be like?
