end of one's rope/tether, at the/come to the

at the end of one's rope

 and at the end of one's tether
Fig. at the limits of one's endurance. I'm at the end of my rope! I just can't go on this way! These kids are driving me out of my mind. I'm at the end of my tether.
See also: end, of, rope

at the end of (one's) rope

/tether
Out of energy or patience; exhausted or exasperated.
See also: end, of, rope

end of one's rope/tether, at the/come to the

To have exhausted one’s resources or abilities. The term alludes to a tethered (roped) animal that can graze only as far as the length of the rope permits. “Being run to the end of his Rope, as one that had no more Excuses to make,” wrote Sir John Chardin in 1686 (The Coronation of Solyman the Third). “I am at the end of my tether” was close to being a cliché by the time Royall Tyler used the line in his comedy The Contrast (first U.S. production in 1787).
See also: come, end, of, rope