best-laid plans of mice and men oft go astray

best-laid plans of mice and men oft(en) go astray,

 and best-laid schemes o' mice an' men gang aft a-gley.
Prov. Things often go wrong even though you have carefully planned what you are going to do. (The gang aft a-gley version is Scots dialect, and comes from Robert Burns' poem "To a Mouse.") Jill: I reserved a hotel room for us three weeks ago, but now the clerk says he has no record of our reservation. So much for our fun weekend in the city. Jane: Well, these things happen. The best-laid plans of mice and men oft go astray. I had all the arrangements made for my party, and then the guest of honor got sick and I had to call the whole thing off. The best-laid schemes of mice and men gang aft a-gley. If a little rain can ruin the best-laid plans of mice and men, think what an earthquake might do!
See also: and, astray, men, mice, of, plan