Probably the most important thing I have learnt over the past 18 months is that truely nothing is certain, no result is ever known in advance, things can change very quickly.
This does not seem all that insightful I know, and if you had have told me this two years ago I would have agreed with you. I only realised that I didn't actually agree with this until I was tested in this belief by having something that I thought would last for ever taken away from me. It was then that I realised I did not want this universal truth to be true for me. I wanted some things to be for ever, against the rules of the universe, because I couldn't handle it if they weren't.
I'm not even trying to be spiritual by saying that nothing is forever. At a cosmic level, the sun will one day consume our planet; the universe will probably collapse in on itself. Even a poor combination of a regulation change in the earth's axis with a small change in its orbit around the sun could leave life on this planet decimated due to rapid climate change.
But realising this truth has been liberating. I no longer feel the need to cling to things or to feel irrevocably attached to them. Things come and things go, and that is okay, and I can actually handle it.
I know there are still ways I am not free of this: the thought of losing all I owned and everyone I loved is not something I want to be tested with. But I have a sense that even those things, as much as I don't want it to be true, are not here forever.