如火如荼似光似毒
[rú huŏ rú tú sì guāng sì dú]
A vivid expression combining two sets of contrasts - fire/flame vs flourishing (荼 normally means tea, but 如火如荼 idiomatically stands for thriving/burgeoning; poison vs light, suggesting complex emotions or experiences, sometimes positive and enlightening, sometimes hurtful and destructive.