Paul's deep, constant, and unresolved grief is a standing rebuke to the shallowness that forbids Christians to grieve on the grounds that all shall be well. Earnest preachers have sometimes read 1 Thess 4:13 as forbidding grief of all sorts, whereas what that passage forbids is grieving of a particular kind ("after the manner of pagans who have no hope"). To hold firmly to the Christian hope is not to pass beyond grief; indeed, not to grieve is not to love, since grief is the form love takes when the beloved is taken away. Paul himself speaks elsewhere (Phil 2:27) of the grief he would have had if Epaphroditus had died ("grief upon grief," he says); no suggestion there of simply "rejoicing that his friend had gone to a better place." As long as death is real, grief is real too. If it is not acknowledged, and expressed appropriately, it can be poisonous.
At the same time, it is vital to learn the lesson that this deep and inconsolable grief can co-exist with the joy and celebration that fill the previous four chapters. The many-layered texture of Christian experience has room for both, and more besides. Learning how to live with these different layers, giving each its proper place, is part of Christian maturity; pointing to this task, and helping people to engage in it, is a vital part of Christian ministry. What happens between Romans 5-8 and Romans 9-11 at the level of literature must be facilitated at the level of prayer and Christian self-understanding.
-Romans, The New Interpreters Bible