For the first time, when I move to cryptocurrency world (March 2016) the btc price were around $400... it was risen up to $17000 few days ago... 17000/400 x 100 = it's 4520% growth in 21 months.
There's a popular statement such as, the thing what it is existing next to the risk is the success.
Should I believe it and do what I didn't do 21 months ago?
Well, you could try but know that the rate of price increase last time will not be the same as of now because bitcoin is more popular than ever. When you first tried bitcoin, it is just starting to gain popularity so many people got hooked on it and started investing for themselves. Right now, you can still invest but you'll probably wait for a long time before seeing some gains.