Final answer:
The client is experiencing normal grief, which includes reactions to the loss of a loved one and can manifest through feelings of sadness, among other emotions. This type of grief aligns with the stages described by Elisabeth Küblber-Ross, although not everyone will experience all stages in a predefined order.
Step-by-step explanation:
The nurse should identify that the client is experiencing normal grief. This type is characterized by the emotional reactions of loss following the death of a loved one. The client's awakening in the morning with feelings of sadness three months after the death of his partner is a typical expression of normal grief.
Normal grief includes a range of emotional responses as outlined by Dr. Elisabeth Küblber-Ross's five stages of grief: denial, anger, bargaining, depression, and acceptance. It's important to note that these stages are not necessarily experienced in a linear fashion and not everyone will experience all stages. In the scenario described, the individual's sadness could be related to the depression stage of grief, indicative of a normal grieving process rather than the prolonged grieving process associated with complicated grief, the pre-loss grieving found in anticipatory grief, or the marginalized grief seen in disenfranchised grief.