Something that helps me put my current problems into perspective:-
In a hundred years time we will all be dead. Strangers will live in our homes and our cars and precious possessions will either have been destroyed or be in unknown hands.
Our descendants will hardly know who we were. How many of us know our grandfather's father?
After we die we will be remembered for a few more years and then we will become memories. A few years on again and no-one will remember us.
I find thinking like this really helps when things are difficult; though depending on my mood, it can also make me feel sad and to ask what's it all for?