The market plays so much with our emotions, the more we learn to trade without our emotions the better for us, and also don't just trade without a strategy, it's very easy to place a trade Buh determining the take profit becomes the issue, I think it's better to set a target and once you hit your target close the trade and never look back because sometimes the market might be decietful.
Taking profit shoudn't be an issue if you already have a trading plan before entering a trade and we're all advice to have one to avoid scenario like what you just said above. You should know your entry points, profit taking point depending depending on how many times you want to take profit or just a one time profit taking. Knowing all this will help you have a successful trade free from emotions.
Sticking to your trading strategy is very important but you should also be flexible in the sense that if there's a change in market direction you should adject to adapt to it. You can't continue been in a trade that isn't profiting you just because you're told sticking to trading plan is important. If the market is heading towards a bearish one then you should adjust to that but wait for a confirmation to avoid been tricked by the market.
In regards to not looking back at your trades, I understand it's a cautious advice to avoid regrets but still each trade has a lesson to teach so maybe looking back to learn form a trade be it a successful or not can do no harm provided you can keep you our emotions in check to avoid it wrongly influencing your future calls.