Suicide is not cowardly, it's a mental state. Telling a suicidal person that they are being selfish or cowardly does not inspire courage, it could even make them feel worse. It’s important to understand that people who are feeling suicidal do not choose to feel that way; their feelings are a symptom of their mental illness.
Research suggests that those who do attempt suicide are not thinking rationally. For example, one study found that lower levels of serotonin, a key factor in brain function related to behavioral control and decision-making, led to inability to make choices, impulsivity, and lack of flexibility.