At various stages of life we all experience feelings or life events that can seem overwhelming and difficult to make sense of alone. How we interpret and respond to these depends largely on our life to that point and the person we have become, but is also influenced by who we speak to about our problems or the information we gather from other sources such as books or the internet.
For example, if a relationship is going through a difficult phase and you feel rather low your family and friends may be worried, sympathetic and supportive, eager to find solutions (wanted or not) or may rapidly change the subject, depending on their typical response. But if you go to a GP and tell them about your sadness, insomnia and lack of enthusiasm for life they are likely to diagnose depression and prescribe SSRIs because their role is to see symptoms pointing to illness and provide whatever remedies are at their disposal.
Looking for advice online can often direct you to long and varied lists of symptoms