How Does Long-Term Investing Actually Work? Confused About Profit Booking & Re-Entry

I've been investing in the Indian stock market for over 3 years, mostly through mutual funds. I used to watch Shashank Udupa’s videos and picked a few stocks like Happiest Minds, Tata Elxsi, and VBL. While I saw good rallies in some, I didn’t book profits on VBL. I eventually sold all my stocks except VBL since I didn’t have time to track them. But when VBL started dropping, I sold it too. Now, I'm only invested in MFs. My confusion: Many investors talk about holding "fundamentally strong stocks" for the long term but still book profits and re-enter at better valuations. Is this how long-term investing actually works? Shouldn't long-term mean holding through cycles instead of selling and re-entering? Would love to hear how experienced investors approach this!