I invested half of my saving ($25,000) into ETH when it was $725. ETH has now plunged to $459. I am very worried I will keep losing money and I fear for the worst. I want to go kill myself

Remember that as long as you did not sell your coins you still not on losing end as you still have chance to recover once the market condition returns to a bullish trend. The $725 price of Ethereum is still achievable and you don't need to be worried and put and end to yourself. It's just money and you can earn much more on that amount if you will learn the lesson why your money had been trapped on the volatility of the market. Nobody can predict the market trend but you can study how it flows and ride the market volatility.