I have been navigating since about 1969 when I started flight school. I have been using GPS since 1992 when it was a breadbox size Trimble and you had to use special charts.

Absolutely the worst time to learn a GPS is when you need it. Like any other tool, you need to know all the functions without having to spends hours in the menus or the manual. When I get a new GPS I use it every day. Use it to go to the market. When you get there, create a waypoint. Then use the waypoint to get there the next time you go. If you have a unit that is designed for off-road use (Lat/Long) don't use it in Streets mode. Those damn signs are a real pain to find in the back country. Learn to input waypoints from a map or a list of waypoints.