The Prophet (peace and blessings of Allah be upon him) said: “The world is a prison for a believer and Paradise for a non-believer.” [Muslim]

A believer is ever mindful of Allah (subhana wa ta’ala). Therefore, he/she is not free to do what they please. They cannot wait to get to Jannah where they will have no restrictions of any kind, no suffering, no sacrifice, and no separation from their loved ones. That is why this world feels like a prison to them. Those believers who are even more cognizant of Allah (subhana wa ta’ala) are in even more pain because of their separation from Him.

An ashiq/lover always yearns to join his Beloved (subhana wa ta’ala). This is the sole thought occupying his or her mind.

You are the true innermost desire of my heart,

Love of You is the deepest thought in my mind.

Whenever I glance at the world around me,

I find that today there was naught but You,

And that tomorrow holds naught but You.

When an ashiq looks around, he finds the heedless people of the world trapped in their desires. To him the world seems like a cage.

On the other hand, a person who is not mindful of Allah does whatever they feel like, or whatever they think they can get away with. There are indeed many things that can be enjoyed in this world. A person who is not looking forward to meeting their Lord, would spend their every moment trying to maximize their enjoyment here, short-lived though it is.

Thus, the non-believer can find this world to be a Paradise. But the believer knows that no happiness here is everlasting and that they are always in danger of falling into the hands of Shaytaan. They, therefore, long to get out of the exam that this world is and into the safety of the grave.