A quick thought... Christians often take a very black and white view of people - completely perfect OR "sinner". I think this often leads to people not noticing all the good in people, even those who don't call themselves "Christians". I see people as not all bad, but a mixture of good and bad.
It's tempting for Christians to think that the good in people is "tainted" by their bad. And this is true in one sense, but adding mud to pure water. But also think we can see true goodness in people despite their other bad character traits. I like to think of the good parts of people's characters as being like nuggets of gold, treasure in the midst of more mundane clay and hard stone. Stones represent bad aspects of character. Clay, though, has potential to be shaped, and I think it can eventually turn into either stone or gold (just go with the analogy here, don't think too hard about the chemistry of that). In other words, as people grow older they create more stone or gold in their hearts - more self-centredness or kindness, more bitterness or joyfulness, more short-temperedness or graciousness...
And the scary and beautiful thing is that I think other people can have a huge affect on what sort of character traits develop in people. Scary because people often promote bad character traits in people, but beautiful when we encourage each other on toward goodness.
So, my thought was simple - see the good in other people and encourage that good in them. Praise them for it, rather than picking on their flaws. Because I think that's a great way to actually help the good in other people grow and at the same time make them feel less gloomy.
PS: If you read this, how about leaving a comment? I like comments =)