Overthinking isn't bad when you're ruminating about something that's generally positive: how lucky you are to have such a wonderful family, the material you want to have down cold for tomorrow's finance exam, the ideal place to propose to your girlfriend. In other words, thinking deeply pays off when it's something that induces positive emotions in you. You imagine yourself succeeding in whatever it is you're aiming for. You're focused on what you have rather than what you lack. If you're consumed with thoughts that breed negativity -- from how stupid you were for turning down that date to how sure you are that you're going to bomb the presentation this afternoon -- overthinking can have an adverse effect on your physical and mental health. It can lead to anxiety, depression, low self-esteem, and other detrimental conditions. It's a fine line to tiptoe. Indeed, we should all strive to adopt a "half glass full" mentality. I don...

Whatever you do, don't harp on the past . Reminiscing is good, but only up to a point. If you find yourself stuck in the past rather than focusing on present and future goals, you're only inhibiting your growth.  Sure, we all have moments where we reflect on happier times in our life and say, "I almost miss those days." But we are prone to such thinking when faced with challenges in the present that drag us down. But why not tweak your thinking and reason that once you surmount those challenges, you'll be even happier -- and feel more accomplished -- than you did in the past? Then there are those of us who ruminate on bad experiences in the past -- a close friend inexplicably stabbing us in the back, a significant other we envisioned ourselves being with our whole lives suddenly proclaiming their need for space and effectively ending the relationship, an outstanding job opportunity that slipped through our fingers. But brooding over the past i...