There is a lot to learn when looking into the past. However you should not think that the past was somehow greater that today.
In fact to live a miserable life just start to think about all the bad things that has happens in the past. You will relive your memories, making them your depressing state of today.
We do not tend to think about the past and the impressive feat that we actually overcame all the obstacles and are still standing.
So take a look at the past and imagine how you will overcome your current obstacle and then how the future will be brighter than before and you will live in a more fantastical world tomorrow – if you start creating it today.