When you have challenges on qualities (especially ‘skill’ type qualities – Brawn, Charm and that sort of thing), don’t talk about how hard the challenge is in the surrounding fiction. If you talk about the ‘desperate, painful struggle’, it will be odd for the player whose character has lots of the relevant quality and a 100% chance of succeeding.
Characters will often end up with qualities at levels you didn’t expect. This is a problem in itself, but it’s made worse when the fiction doesn’t match up. So, don’t reference how hard a problem was, just that there was a success or a failure. If you want to emphasise how difficult something is, it’s better to give it a cost.