You're late for work, you've a meeting to get to, you grab a slice of toast on your way but Sod's Law means you drop it butter side down on your suit. Similar scenarios happen to the people up and down the land and it's always blamed on the law of Sod - when things go wrong at the wrong time.
But now a Cardiff University lecturer has produced a mathematical formula behind the "law" and how to avoid it.
Inconvenience and background stress were found to influence if it happened.
Dr Cliff Arnall, a psychologist based at the university's centre for lifelong learning, has already drawn up a formula for the happiest and saddest days of the year.
He calculated out a Sod's Law formula for an insurance company.
During his study he worked out using six factors, based on state of mind and the impact of the task going awry, that preparation was crucial in avoiding being a victim of Sod's Law.
The formula uses:
* Task Importance (Ti)
* Inconvenience, and financial and emotional cost of task not going to plan (I)
* Optimism - the tendency to think everything will work out fine (O)
* Background Personal Stress Levels (Sb)
* Extent of Planning (P)
* Memory - especially for things that worked out well
Using a scale of 1-5 for each factor, the minimum chance of Sod's Law striking is a score of 0.3 and the maximum is a score of 17.5.
Mathematically, it is expressed as:
1/8Ti x I 3/8 + O + Sb
P + M
"There are a number of common mistakes we make when planning a task, all of which contribute towards the likelihood of something going wrong," said Dr Arnall.
"Sod's Law tends to strike in direct proportion to the importance of the task.
"Other factors such as planning ahead and the inconvenience of said task not going to plan are also crucial.
"The formula uses both emotional and organisational factors, because mental impact and the ability to foresee possible problems - and make provisions for these - are the enemies of Sod's Law."