Corrections are fairly common in the Bitcoin market and it is healthy. Is Bitcoin overvalued or undervalued is what market decides and random periods of short-term corrections is a necessity for long-term stability. What we are going through now is another correction, a decline of around 25%. Historically, Bitcoin has gone through a decline of 94%, 85%, 76%, 72%, 49%, and recently 39%.
Bitcoin is a long-term investment. Short-term gains, a decline in price, getting panicky, selling, then Bitcoin really isn't for you. Corrections are a good time to buy some cheap bitcoins.