Trend lines are great for focusing your attention on a possible level that the rest of the market may react to. They are not in any way magical or absolute, they’re just a very good indicator for timing certain trades. You could wait for rejection as a trading methodology, which in combination with other elements like fundamentals, sentiment or other indicators could see you stay in a trend for the majority of its natural duration. Or you could wait for a break, retest and continue in the opposite direction. How the price is reacting to previous areas of supply and demand is key to that decision. Along with the macro drivers of the asset you’re trading.
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