You've been following some of the top coins such as Bitcoin, Ethereum, Dash, Ethereum Classic, but you always thought to yourself that you were "too late" and that the they were already expensive. Well, today is Christmas!
Let's take the example of Ethereum:
Ethereum is currently priced (as of right now!) at 279 USD, which is the price it was at on June 9th. This is a coin that has known tremendous growth and has a huge marketing machine behind it. It has gone as high as 412 USD on June 12th. Now is your lucky day. I own some Dash, ETC and Golem but had never bought any Ethereum because I didn't believe that it go up that high. Boy was I wrong. Now I've stocked up on a load of Eth at a discount price. 
It's highly possible that Ethereum could still go down in the following days but everybody that has been in Cryptocurrency will tell you, good coins always recover and reach new highs. So now is the time to buy some more. It's sale day!