My first "solo" IMC was a training trip as a brand new captain with a brand new copilot. On departure we had the wrong NDB tuned in (256 instead of 266 which where two miles apart, hard to tell when they were on the same rough bearing). After ATC kindly informed us we were two miles north of track, we had a radio failure right where we'd flight planned an altitude change. Copilot changed altitudes while I was heads down sorting out the comms issue. Just as I got terminal up on a backup radio they politely informed me we had descended without clearance. Later as we are breaking out from the enroute ILS at 400' it occurs to me that this is substantially lower then the 1000' or so forecast and our destination (NDB only) requires 600'. We amend our route to try to get into the home base (which is at minimums now despite the VFR forecast) with enough gas to divert if necessary. During the approach at MDA in heavy rain my wipers fail (thank you Bell for those wonderful things) and the NDB goes intermittent. Just as I am about to overshoot we become visual with the pad and land.
The only system that didn't fail me that flight were the engines and I am forever grateful to have learned all those lessons, the hard way, early in my career. Now I never trust the weather or rely on Bell wipers and always confirm the copilot's navaid settings.