As someone who's worked in the UI automation field for approaching 10 years, getting it to not break takes a little of (1) knowing what actual user interactions

As someone who's worked in the UI automation field for approaching 10 years, getting it to not break takes a little of (1) knowing what actual user interactions look like, (2) knowing how UIs commonly break, (3) knowing how the underlying UI framework commonly breaks / what shortcuts programmers are apt to take (e.g. simulated async in VB6), (4) knowing how events and code interact in a running system, & (5) striking the proper balance between performance and reliability. Honestly, though, 75% of automation errors are timing missteps -- automation dispatching events at a specific millisecond that a human never would.