I use formal risk assessment methods a lot for professional purposes - for example planning test flying, taking work teams to "complicated" parts of the world, and so-on.
However, the place for this is NOT where I'm about to embark upon an individual flight. There are good practice / CRM / Airmanship techniques to use before a flight - these can pretty much be bracketed under the heading of "checklists".
However, to start thinking hard about things like risk assessment matrices before an individual flight means that you aren't thinking properly about the detail of the flight - it's a time for simpler tools.
G