One of the misunderstandings about depression is that it is all about feeling down and miserable but you can be like that without depression. Depression is where you don't control your emotions but they control you so you swing between highs and lows without being in control.
The most useful advice I have received is this:
For those of you who don't know this is the Mersey ferry which crosses the river Mersey between Liverpool and the Wirral. What is important about the ferry is that the river is tidal which makes it harder to steer the ship directly from one side to the other.
Now what, I hear you say, has this got to do with depression. The answer is in the ebb and flow of the tide over which the ferry has no control. If the tide is flowing in the ferry has to be steered downstream to arrive at the right place and if the tide is flowing out the ferry has to steer upstream. It is the same with depression if it is pushing your mood high you have to steer it back down and if it is pushing you down you have to steer it back up.
Now I'm not saying I've mastered this because so far all I am able to spot when I'm getting too 'high' and have been able to bring myself back to an even keel. (Too high is dangerous because it leads to a crash.) So far I'm not very good at noticing the much slower signs that lead to a 'down' but I'm learning.