It could be related to your medications as well and even though you are feeling better you could still have a lingering of the depression. But if you are feeling quiet bit better I would say it may just be habit and agree with dragonfly2 regarding some of the ideas to break the habit. Wishing you well.
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Bipolar I, Depression, GAD Meds: Zoloft, Zyprexa, Ritalin
"Each morning we are born again. What we do today is what matters most." -Buddha