To be your best self; the time in your life when you are at your best, most successful, funniest, coolest, most popular

Lying flat refers to a defeatist lifestyle in Chin, where people stop working, desiring material acquisition, and tap out of any social life – sometimes for good. By lying flat, young people are participating in a kind of non-cooperation movement, rather than surrendering themselves to China's oppressive work culture where they see little hope of social mobility.

peaked.. you peaked from coolest to complete total loser

Being at the peak of a high from cannabis or other drugs.

looking pale as a result of sickness..

the feeling after ingesting copious amounts of pain killers

To hit orgasm. Climax.