I also want to explain that there is a difference between feeling sadness or experiencing hardship and depression. To call someone weak because they decided to end their life, then trying to justify it by saying everyone experiences hardships and need to be able to handle it better is not a very accurate comparison.
Sadness and depression are not interchangeable.
For example, to lose a loved one such as a parent may cause immense sadness. It may last for a very long time, but the person suffering may not necessarily develop clinical depression.
On the other hand, someone with seemingly no problems may develop a form of depression. I can use my own personal experience for this. I am 20 years old, I have never lost anyone close to me, I have great family and home life, I've been raised reasonably well-off my entire life - However I have lived with an anxiety disorder for a large part of my life, and I have suffered from clinical depression for the last several years.
To describe depression as just being sad is a severe understatement. It's a feeling of complete disinterest. Feeling lost, useless, constantly in a state of "blah". Some days are better than others, you can feel normal, you can feel happy, but it doesn't always last long. There is nothing worse than being surrounded by people that don't understand, to have people constantly tell you to "get over it". To be asked why you aren't able to just "get over it" when you don't understand why yourself is very frustrating and confusing.
If you do know someone that suffers from depression, please take the time to understand what that means - Don't just assume they are weak or handling life poorly.