Time-to-market pressure is the pressure to deliver a good product quickly. It is good because it reflects a financial reality, and is healthy up to a point. Schedule pressure is the pressure to deliver something faster than it can be delivered and it is wasteful, unhealthy, and all too common.
Schedule pressure exists for several reasons. The people who task programmers do not fully appreciate what a strong work ethic we have and how much fun it is to be a programmer. Perhaps because they project their own behaviour onto us, they believe that asking for it sooner will make us work harder to get it there sooner. This is probably actually true, but the effect is very small, and the damage is very great. Additionally, they have no visibility into what it really takes to produce software. Not being able to see it, and not be able to create it themselves, the only thing they can do is see time-to-market pressure and fuss at programmers about it.
The key to fighting schedule pressure is simply to turn it into time-to-market pressure. The way to do this to give visibility into the relationship between the available labour and the product. Producing an honest, detailed, and most of all, understandable estimate of all the labour involved is the best way to do this. It has the added advantage of allowing good management decisions to be made about possible functionality trade-offs.
The key insight that the estimate must make plain is that labour is an almost incompressible fluid. You can't pack more into a span of time anymore than you can pack more water into a container over and above that container's volume. In a sense, a programmer should never say ‘no’, but rather to say ‘What will you give up to get that thing you want?’ The effect of producing clear estimates will be to increase the respect for programmers. This is how other professionals behave. Programmers' hard work will be visible. Setting an unrealistic schedule will also be painfully obvious to everyone. Programmers cannot be hoodwinked. It is disrespectful and demoralizing to ask them to do something unrealistic. Extreme Programming amplifies this and builds a process around it; I hope that every reader will be lucky enough to use it.