Fun game! Maybe one day I can get over my skill issue and actually beat the easy difficulty consistently
It's normal to be bad at first :-).
Always play the easiest difficulty until you start beating it consistently.
If you think about it, you are essentially trading HP for EXP. So you want to maximize the impact of each HP.
Ideally you will use your HP to uncover unknown cells. But you want to do it intelligently. If some dirt says 8, and you have 6 HP, and a 2 monster is revealed, then you know it's safe to hit all the unknown cells around the dirt. If a 5 is revealed, then you know the remaining one is 1 -- so don't reveal it, just mark it.
This is the sort of thinking you must do.
Always open chests immediately, but don't refill your hearts until you've spent them all.
Some monsters are special, like the mummy -- try to figure out the pattern of how the mummy is placed. Then you can locate the mummy early, kill it, and get a nice bonus.
Good luck!