It always takes longer than you expect. (Even when you factor in Hofstadter’s law.)
When a measure becomes a target, it ceases to be a good measure.
A complex system that works is invariably found to have evolved from a simple system that worked. A complex system designed from scratch never works and cannot be patched up to make it work. You have to start over with a working simple system
Any code of your own that you haven’t looked at for six or more months might as well have been written by someone else.
Any organization that designs a system (defined broadly) will produce a design whose structure is a copy of the organization’s communication structure.
Adding manpower to a late software project makes it later.
The overall performance improvement gained by optimizing a single part of a system is limited by the fraction of time that the improved part is actually used