Overstep the mark/line British American phrase
In this expression, the 'mark' may be the line behind which runners stand prior to the race. Alternatively, when a line was drawn in the ground that neither boxer was able to cross, it may refer to boxing matches in the past.
To go further or do more than what is allowed
She will lose her temper, if you overstep the mark.
I shouldn't have overstepped the line, so I hadn't been punished
It is often used in all of tenses.
There is no clear information about the origin of this expression.
A humorous way of saying that what one has said is just what they acknowledge and may not be entirely accurate
Mike: Have you returned from your vacation on the beach? Your skin seems to get tanned.
Jenny: My skin is always dark. That's my story and I'm sticking to it!