Don't start strong and finish weak — see things through to a good end.
Tips
history
First recorded in Song-dynasty Zhu Xi's 《朱子语类》, where he criticized Ouyang Xiu's preface for promising much at the start but trailing off at the end — 'not stopping short of dragon's head, snake's tail.'
memory
Picture a creature with a magnificent dragon's head and a thin snake's tail — impressive opening, anticlimactic ending. Near-synonym: 虎头蛇尾 (hǔtóushéwěi), 'tiger head, snake tail,' which is more common today.