This is vital enough in CS/engineering but also in life. U can't do it for everything but at least for the things that matter to you or things that you can do it for cheaply (time/effort) and can yield greater results.
- Back up plans
- Disaster plans
- Legal/financial
- Second opinion for doctors
If you’re into this kind of thing try reading Simple Rules by Donald Sull & Kathleen Eisenhardt.