It's not unusual to have ups and downs in the course your life. However when these "down" parts take a deep dive it can feel much more difficult to come up. This is one difference from having the "blues" and depression. The down part may feel like you have a ton of weight on your shoulders, your every thought is negative or hopeless, nothing (hobbies, people, food) is enjoyable as it used to be, you can't sleep or can't stop sleeping, and life just does not matter anymore. The deepest feeling you may have is despair that lingers for weeks and you just have a longing to end this torture. Depression can happen to anyone. It's a silent sickness because it's hard to admit feeling crappy when there appears to be nothing physically wrong with you.
The truth is, there are so many things that could happen in our lives that can bring on depression these days. We really have more at stake with the kind of lifestyle that we have. Loss of a job, loss of a family member/child/friend, divorce, infertility, infidelity, chronic pain or illness, and the list goes on. So I suggest for you to equip yourself with the best ammunition that you can for dark times in your life. This ammunition includes: a support system of individuals that you can vent or pour your heart out to, a routine for physical activity, a routine for self care that is positive, and a daily dose of positive thoughts. Having many outlets can help when depression sets in and one or more of these outlets are compromised.