Between weather and travelling I ended up with only 3 real rides in April. After a winter of 1-2 indoor strength/power interval sessions per week killing my endurance enough, April just destroyed me. I'm physically stronger than last year by quite a bit, but I can't make use of it because my base wasted away. Rides that were routine in September are pretty tough right now.
Watching my power numbers on hill repeats I should be at or near my personal best (and I was in mid-March), but two of what I would normally consider relatively trivial group rides on the two days before repeat night just leave me wrecked. I'd lost about 60% off my comfortable ride distance.
It comes back quickly enough, though, if you let it and stay on top of your recovery/rest. Just ride to the same perceived effort and you'll get back to where you were. It's pretty hard to keep from beating yourself up about it, but it's just the way things work. When your base fitness gets back to where it was all of your gym work will pay off and you'll be ahead of where you were.