You can try to be happy by keeping your head in the sand. That is, to live in escapism, often taking the form of idealism.
However, reality will slap you on the ass, and once again your happiness will be stolen from you.
The other approach is clear eyed bravery: to see reality as it is, or at least as much as you can understand. This is not being a cynical realist; it is seeing through your own illusions and delusions.
Once you can see through yourself, you can see through anybody – and not being tricked, you can love them; then you will never not be happy.