If a stock trader fully depends on technical analysis, how can he react to anything happens at non-market hours that his graph does not show until next day morning?
Is this a demerit being a complete Technical Analyst?
You can't. Even as a technical trader you should know what events are coming up and be prepared. You can't prepare for everything but you should know when the earnings dates are. You should also pay attention to the market in general.
Stocks also have personalities and you should get to know that personality.
Most important thing in trading is deciding when to get out before buying and stick to it when it goes against you. It is also one of the hardest things to do.