A trend is a sequence of swings, not a feeling about direction. A break of structure confirms it continues; the shift happens when the one swing the trend was standing on finally gives way.
What confirms a trend — A break of structure: price taking out the prior swing in the direction it is already going. Until that happens, the move is a move, not a trend.
What protects it — The most recent higher low in an uptrend, the most recent lower high in a downtrend. That single level is what the read is standing on.
What ends it — That protected swing breaking — not a large candle, not a failed push. A lower high is a warning; the shift is the break.