The self-preservation instinct and general human will to live is strong enough to keep you going even in the absence of "enough good things". But good things aren't the only thing that balances out bad things, as anyone who has seen authoritarianism first hand could tell you. Bad things squared can work just as well.
For example, most religions have a taboo on suicide. "Your life sucks? Well tough shit bucko, you choose the easy way out and you end up in hell where it's infinitely worse forever." Absurd as it may sound, people can live against their will, too.
For example, most religions have a taboo on suicide. "Your life sucks? Well tough shit bucko, you choose the easy way out and you end up in hell where it's infinitely worse forever." Absurd as it may sound, people can live against their will, too.