That is marred by the memory of having to reload the assembler program from cassette every time I made a mistake in the machine code I was trying to learn.
That feeling of despair has stayed with me a long time
From memory I could successfully load from and use about half the tapes I ever bought for my speccy, and I still don't know whether it was me or them.
Worth it, though.
Then there was those tapes where that alone wasn't enough due to how much the head would move as per screw position, so in addition I might need to use a screwdriver to move the tape holder just a couple of millimeter more on top.