Advise for Holding BTC When it Falling

Why BTC falling?
First of all, no one knows for sure. But below are a few reasons at play:

Current Supply: Roughly on every 10 mins, 25 new BTC are issued as block reward. At the current price of BTC, that's ~$830K new BTC a day (25 x 6 x 24 x 230). As many miners sell most of the block reward to recoup the cost of mining, for bitcoin's price to remain constant, these new BTC have to be bought by market participants.

Demand: While the number of transactions is trending upwards, it seems that there is not as much new interest in investing into bitcoin at the moment. Interest has stabilized, but may not be outstripping demand.

Risk: In addition to the price risk from the fluctuating exchange rate, there is currently a very heated debate about the bitcoin 'software' with competing proposals on how to scale bitcoin in order to facilitate more transactions (BitcoinCash, BitcoinGold). Without going too much into detail, the discussion questions some of the core principles of bitcoin.
So do I believe Bitcoin will prevail? Absolutely. It will also probably make a great long-term investment, but in the short term, the price may even drop further. A few things may help a rising price:

More use cases, e.g., services utilizing BTC
Halving of the block reward to 12.5 BTC, due mid-2016(Bitcoin Clock)
Settlement of the "scaling debate"
A rising price (this sounds funny, but a raising price itself will fuel additional demand).
Absence of catastrophic events (bugs in the code, network failure, etc.)

In the end, you need to be comfortable with your investments and the risk that you're taking.