Ever heard of the phrase:
"Time in the market beats timing the market"?
What it means is to buy fundamentally good stocks / ETF for long term and dollar cost average into them.
Just take a look at $SPDR S&P 500 ETF(SPY.US)$ over 10 years. 
The dips may last for a few months, but after those dips, it's back to all time highs.
The reality is, no one can time the market consistently. Trying to do so is simply gambling with a coin flip...