I keep accidentally spending sugar lumps, especially during cookie storms. It's not impossible to work around, as you can keep the Stats page open most of the time but still, it's super frustrating when a once-per-day currency is accidentally spent on +1% cursor CpS and then the game happens to save.
Is it possible to make spending a lump a little harder? Maybe a prompt? Making the thing you need to click hidden behind something? Maybe some kind of dragging action?
I realize there may be situations where you would want to quickly spend a lump on magic or something, but I have yet to accidentally spend a lump on magic or swaps since I can keep the Grimoire and Pantheon closed. It's the building levels that are an issue.