I think I'll try with spells now. Another reason for me saving items is loss aversion, that cognitive bias heavily influence how I play lol: https://en.wikipedia.org/wiki/Loss_aversion
Who are the most rage inducing enemies?
I played it some more and it's not a particular enemy, is because when there's almost no space left, there's no time to move to left/right because of the delay, and the rest of the pieces just get stacked almost immediately.