Physics is unimpressed by your bravado, intolerant of your negligence, and unaware of your time schedule.
Perhaps my favorite show on TV is "Modern Marvels". I particularly enjoy their series on Engineering Disasters. I'm not a real engineer, but from what I can tell, engineering is really about understanding failure points and how to avoid them. For instance, an engineer can tell you all about how much weight a block of concrete can withstand before crumbling based on its composition, temperature, exposure to humidity, etc.
Since I've watched a lot of the engineering disasters episodes, I thought I'd summarize the things that are at the heart of most engineering disasters:
Bravado. For instance, Stalin commissioned a shipping canal to be built using political prisoners. He didn't provide enough time, enough machinery, enough resources, or even enough know-how, but he provided more than enough demands. He ended up with a useless, fragile canal and many thousands of deaths.
Impatience. If you are in too much of a hurry to fortify the concrete in the correct manner or to inspect all of the welds carefully, something is going to break. It doesn't matter how many women you get pregnant, it still takes about nine months to make a baby.
Ignorance. A big part of engineering is knowing how things have failed in the past and how to avoid making the same mistakes. Everyone knows about "galloping gurdy". That was a lesson about harmonic motion. There are similar lessons to be had concerning the brittleness of steel at extremely low temperatures, concrete when dry, iron when exposed to the elements, the danger of pure-oxygen environments, etc. That which you don't know can still kill you.
Negligence. Often, there are signs of a problem, and they are ignored. For instance, a steamboat captain might override the pressure valves on a steamboat leading to a boiler explosion, or chronically neglected routine maintenance at a chemical plant might lead to a cascade of failures leading to a catastrophic failure. If you ignore a problem, it won't go away--it'll probably get worse.
Overloading. For instance, the Air Force had a successful plane. It was engineered for a specific engine, and it was successful with that engine. Later, they took the same plane and strapped on an engine that was more than two times as powerful. The plane couldn't handle the added stress and it came apart catastrophically. If something behaves well given certain constraints, it probably won't continue to work well if you ignore those constraints.
Multiple. For instance, there was a crane accident. The crane was at its limit of weight, but the operators were negligent or ignorant of the impact the wind would have on the operation. They were impatient, so decided to move ahead instead of waiting for conditions to improve. Multiple people died. Here's a quote from the show, "All great engineering disasters are the result of more than one failure." Very often, multiple small problems, each caused by any of the above, can work together to create a catastrophic failure.
And, of course, all these same lessons apply to software engineering.