Day trading can definitely be profitable and especially with BTC because of the large swings.
Where there is chaos, there is money.

Places like bitfinex let you short the market which is a fairly important option if your day trading.. As market movements are mainly led by news you should arm yourself with a good news aggregator like BitcoinWire.net and charts like bitcoinwisdom.com.

RE investment - this should always be what feel comfortable loosing. Never let your emotions take control of your trades.

HTH