Experiencing the death of a loved one
Experiencing a divorce or break up
Losing one's job
Realizing the death of a dream
Losing one's home
Loss of one's health via a devastating diagnosis or accident
Losing a limb or one of the five senses
Experiencing a loss of mental aptitude (due to a disorder, an accident, aging, etc.)
Losing one's freedom—through incarceration, being enslaved, because of an oppressive ruling regime, being placed in an assisted living facility, etc.
Being banished from a group, family, church, etc.
Losing one's innocence, through disillusionment, being let down by someone, abuse, or some other means

There are five basic human needs that, when missing from a character's life, could motivate them to pursue this goal. The following needs are all possibilities, but only one of them should be the primary driver for any given character. For more information on the relationship between human needs and outer motivations, please see this Character Motivation tutorial.

Self-Actualization: If a character realizes that their response to a loss is keeping them from achieving their goals and dreams, they may be motivated to face their loss and adjust their response to it.
Esteem and Recognition: Many times, a loss can impact a character's sense of self-worth. This can happen when someone loses a job or lover or something for which they feel culpable. When they reach rock bottom and decide they want to feel better about themselves, they may choose to address their situation.
Love and Belonging: Every one responds differently to grief. If a character's reaction to loss has resulted in them becoming isolated or disconnected from others, they may realize their need to address their loss in order to regain that connection with others.
Safety and Security: Grief can hit some people harder than others. If a character's health or well-being is impacted, they may find themselves pursing the goal of dealing with their loss in a healthier way.
Physiological Needs: