A new play opening this week at Bushwick’s Unit J says the best time to face grief is when it’s staring right back at us. The winner of a Dutch playwriting award a decade ago, Lot Vekemans’ “Poison,” made its off-Broadway debut seven years ago at the Beckett Theatre. Now, the story will unfold in a very small and intimate space in Bushwick, epitomizing what some critics have called the play’s “fiercely claustrophobic” nature. Hosted inside the home of local actor Richard Carrillo, which he also uses as the Unit J “performance space,” his tear-jerking performance offers an intimate look at loss itself.