Be thine own palace, or the world's thy jail.

La mente es tu propio palacio y puede hacer un infierno del cielo o un cielo del infierno” – John Milton, El paraíso perdido.

Study the prison you have inadvertently built around yourself.

Build therefore your own world.

You are all in jail. Each alone, solitary, with a heap of what he owns. You live in prison, die in prison. It is all I can see in your eyes – the walls, the walls!

The world is a prison in which solitary confinement is preferable.

If you're going to be a prisoner of your own mind, the least you can do is make sure it's well furnished.

make sure
the walls
you build
to protect yourself
do not become a prison

The World exists for you ; Build therefore your own world

Those who build walls are their own prisoners.

...most of us build prisons for ourselves and after we occupy them for a period of time we become accustomed to their walls and accept the false premise that we are incarcerated for life. As soon as that belief takes hold of us we abandon hope of ever doing more with our lives and of ever giving our dreams a chance to be fulfilled. We become puppets and begin to suffer living deaths. It may be praiseworthy and noble to sacrifice your life to a cause or a business or the happiness of others, but if you are miserable and unfulfilled in that lifestyle, and know it, then to remain in it is a hypocrisy, a lie, and a rejection of the faith placed in you by your creator.

The mind is its own place, and in itself / Can make a Heaven of Hell, a Hell of Heaven. / What matter where, if I be still the same...

Rejoice that you are in prison. Here you can think of your soul.

This is the world you have made yourself, now you have to live in it.