1) 'Sell in May and go away' , this is the common saying that has been around for years.
Picture courtesy of http://www.ritholtz.com
So as you can see, based on the US's S&P 500, if you sell in May and buy back in Nov, you will generally do better (though one thing to note is that, on average, all months actually generate positive returns). In Singapore's context, I am not very sure, but I guess that it should show a similar trend as the world's economy are interlinked.
Picture courtesy of http://blogs.timeslive.co.za
I have also read reports that during the world cup period, stock markets will drop too. This is because people will be pulling money out of stocks to bet and/or spending more time watching soccer and hence not be as participative in the stock market. These reports were also supported by accompanying statistics.
Though I do not believe 100% what these reports have said, I do believe that they should be some truth in it, considering the statistic were not faked.
In conclusion, statistically, it is not a good time to hold stocks over the next few months. Personally, I have sold away around 80% of my holdings, leaving behind some preference shares which I few should be relatively non-volatile.
Also, besides the above 2 reasons that I have mentioned, I am actually going overseas for my grad trip.(Will be visiting Malaysia and the Shanghai World Expo) Thus without the time/access to my trading accounts, I would rather take my profits and have a peace of mind during my trips.