For investors: $TWTR faces major upside resistance. Don't touch it unless it fits into your trading plan or unless you see some upside momentum because there are better investments out there.
Your trading plan should tell you what to do not only when the market is rising, but also when it drops
Remember that the market always goes down faster than it goes up
Your reaction to the market should be automatic
If you find yourself paralyzed not knowing what to do your trading is not working
If you find yourself thinking too much about your next move then you need a new trading plan
Here is an example of a trading plan rule:
Identify support and resistance levels. Exit 50% of your positions if the market falls 1% below your 1st major support level. Exit the remaining 50% if it falls 1% below your 2nd support level.
If you followed the above rules you would exit 1/2 of your positions at $201 and 1/2 at $198.
You should also have rules to tell you when to enter the market which could be the opposite of the above or whatever rules that work for you.
The above is just an example. Your trading plan and rules should fit your investment style and personality.