Buy/sell with set profit in mind or exit strategy

Usually I buy stocks based on companies and what they are doing vs future. For example palantir, Shares I entered 20s with about 50 shares couple of months ago and it touched 80. Do you all sell at that original shares cost and some profit to cover for taxes? Is that the best way and re- entering again if it falls below a certain range? Is there any benefit to holding and not selling it. Now it is back to 60s. I did not predict it would go that high but now I feel as I lost on my paper gains. But again I don’t know where to put full stop and exit out if it is going up. I tried stop loss and trailing losses but they actually negatively impacted as I sold at low price of 10-12% and the price shot back up. So, any ideas on who you all plan/execute these? Thanks much!