Long term investing question.

To start this thread off I do value investing, I look for good long term stocks which pays dividends and has good P/E, P/B, Debt-to-Equity, etc. Now the question I have is if the stock I plan on holding for long term does good and has a 25% gain or more, should I sell it and buy the stock again to lock in the gain? Or should I just let it sit and continue to just rack up the dividends? Still an amateur when it comes to the stock market and have been investing for 3 years inconsistently till now, so any form of advice will be helpful. Thanks!