Don't feel bad... it is probably more worn parts than shifting on the go that caused this to happen.
When you have the cover up, inspect the gates for wear. If bad, they can be removed, built up with a welder and ground smooth.
The wear could also be in the socket ball for the shift lever- this is very common on the A-630 and B-530 with 6 individual gears. Replacing it would most likely save you frustration in the future.
I'll probably roasted for this, but proper speed shifting with a two-cylinder can be done with no negative results if one knows what they are doing.
I hauled forage boxes with two -cylinders for 25 years... if you tried to start from a dead stop in road gear, figure on adjusting the clutch about every 3rd load.
Keep in mind that all sorts of old trucks never had gear sycronizers! Just a skilled operator that new how and where to shift, how to double clutch, etc.