Down the toilet
浪费或失去某物

经常与go/went连用
有时也有一种“可惜”的感觉
好像“某物”掉进马桶冲走了

His whole career went down the toilet because they found out he cheated on his college entrance exams. He'll never work in this industry again.
他整个职业生涯都毁了，因为他们发现他大学入学考试作弊了。他以后永远都没办法干这行了。

Down the drain
白费了，浪费了
意思和down the toilet一致
这里drain就是“下水道”

Well, all my money went down the drain because I listened to your investment advice.
我所有的钱都没了，因为我听了你的投资意见。

Squander
挥霍，浪费（金钱，时间）

You squandered all your savings on a new car. Where will you live?
你把你所有的积蓄都挥霍在这辆新车上了。你以后住哪？

Miss an opportunity
错失机会/错失良机
opportunity of a lifetime
一般指“千载难逢的机会”

I've missed the opportunity of a lifetime because I was too worried about failing.
我错过了一个千载难逢的机会，因为我太害怕失败了。

Throw it away
扔掉，放弃，付之东流
这个刚发一般是“抽象的说法”

You're throwing away your promotion just so you can be with a coworker you like. I think you're making a big mistake.
你为了跟同事谈恋爱就放弃了晋升的大好机会。我觉得这是个天大的错误。

Kiss something goodbye
永远失去某物，说拜拜
这里something可以是很多东西
比如：your 6-pack 你的六块腹肌

If you continue sitting on the couch all day, you'll be kissing your girlfriend goodbye. No girl wants a lazy man.
如果你再继续这样天天坐在沙发里，你就可以跟你的女朋友永别了。没有女人喜欢懒男人。