"Blessed are those who mourn, for they will be comforted."

"They who grieve are blessed, for God will comfort them."

Grieve comes from the root "grave" or heavy. I truly believe Jesus is inviting his followers to see that the Kingdom, the Kingdom of truth, beauty, completion and triumph, involves embracing the heavy weight of the messiness of humanity. Jesus became flesh...the son of God was tempted in every way here on Earth. He experienced the fragility of our skin. He saw our brittleness firsthand. So he invites his followers to grieve for those who are hurting, mourn for those who are broken...because he knew this is our natural condition without His restoration of us. 

So He says...

Mourn for your enemies. 

Grieve for your rival. 

Mourn with your mom. 

Grieve with your estranged wife. 

Mourn with the very person you want to curse. 

Grieve for the lost. 

For you will be comforted.