You might remember the meaning of the character 害 with this easy mnemonic:
Didn't mean any harm? Want to slap that lying mouth (口) for lining (丨) up my one (一) of a kind figurines on the roof (宀) and pushing them off! Thank goodness two (二) survived.
Using mnemonics to remember the meaning of Chinese characters like has a huge impact on how long to learn Mandarin it takes.