ਕਬੀਰੁ ਮਰਨੇ ਤੇ ਜਗੁ ਡਰੈ ਮੇਰਾ ਮਨਿ ਆਨੰਦੁ ॥ ਮਰਨੇ ਹੀ ਤੇ ਪਾਈਐ ਪੂਰਨੁ ਪਰਮਾਨੰਦੁ ॥

I have said many times that literal translation completely looses the real message of GURBANI. Literally KABIRJI is talking about physical death. As you mention how can one find joy in physical death. Let us ask KABIRJI. He says MARNE HEE TE PAEEAI POORAN PARMANAND meaning meaning i find supreme bliss , ANAD in this death. What kind of death is this. Ask the GURU. GURU says SHABAD MARO PHIR JEWHO SAD HEE meaning understanding, internalizing and becoming SHABAD, Spiritual enlightenment gives you everlasting, eternal bliss by killing ego. KABIRJI in this verse is saying people find it most difficult, arduous task to kill ego, individual self. People are afraid of walking on this path, but I have found supreme bliss , ANAND in this spiritual journey