You might remember the meaning of the character 憾 with this easy mnemonic:
The moment I picked up the lantern (忄) and slashed (丿) my halberd (戈) through the enemy's head, I felt one (一) mouth (口) chomp down on my leg and I felt regret in my heart (心).
Using mnemonics to remember the meaning of Chinese characters like has a huge impact on how long to learn Mandarin it takes.