People don't share the darker aspects of their lives online. What you see is the highlight reel. It's important to internalize this, because of the unfortunate tendency for people to compare themselves with others.
If you're comparing yourself to anyone let alone a caricature, you're psychologically doomed. However, simply knowing this fact intellectually doesn't prevent your mind from drifting in the negative direction. For some people it takes a lot of effort. Some people have a predilection for negative thought patterns. I would know. I have done battle with depression my entire adult life. Having the knowledge that negative thought patterns are maladaptive and deleterious to my well being does not always stop the mind from going in that direction. However, after much practice, I have gotten to the point where i can keep depression at bay by consciously steering my thoughts--to the point where it's like i'm teetering on the precipice of light and dark, slipping fully into the dark side much less often.
And that's about as personal as I'll get. I don't really share much about my personal life online. I'll talk about depression because it is a topic that has become mainstream and people are encouraged to talk about it now, and that's a good thing. But there are many aspects of my personal life I'd never think of sharing online. So what you see on Twitter, or my blog, or YouTube--that's just a glimpse. Only the people who are close to me IRL really know the depths of what goes on with me day to day.
If more people opened up about the hard stuff, the gritty stuff, I don't necessarily think it would have negative results. Honestly what I'm most afraid of is being ignored. When you share something personal online, it makes you vulnerable. This probably sounds paranoid but you should just assume there's always someone out there rooting for you to fail, and wouldn't hesitate to use sensitive information against you. These are the potential negative consequence of sharing something sensitive online, but the positive consequences can outweigh the negative if enough people respond positively with support. But if it's ignored, or missed, if there's no groundswell of positive support, then all you've done is expose yourself to the negative consequences. So this is why I wouldn't recommend getting too personal online unless you're in a very desperate situation.