了
le
了 is not finished, it is a line you just crossed
The picture A line chalked on the floor, and the moment your foot lands on the far side. Before the line and after the line are not the same.
Where the picture shows up in 了
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the action crossed over
我已经交了报告。
wǒ yǐjīng jiāo le bàogào
I have already handed in the report.
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the weather crossed over
下雪了，路上小心。
xià xuě le, lù shang xiǎoxīn
It is snowing now, watch your step.
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your mind crossed over
我不想去了。
wǒ bù xiǎng qù le
I do not feel like going anymore.
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the amount crossed over
太贵了，能便宜点吗？
tài guì le, néng piányi diǎn ma
That is too expensive, can you come down a bit?
太…了 has nothing to do with the past. It says the price stepped over the line you could live with.
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crossed and still going
我在这儿住了三年了。
wǒ zài zhèr zhù le sān nián le
I have been living here three years now.