I am a firm believer in these two sayings, and I think having the sort of mindset they give you is a great way to look at things. If something doesn't go the way you envisioned, there isn't much point lingering on that...it clearly wasn't planned to happen that way!
I also think that having this sort of outlook is a good way to remain positive about things. For example, my recent garcon-related events could have left me upset/sad/depressed/annoyed/angry etc etc, but I refuse to let it. I see no point in lingering on the 'what if's' and agonizing over how things didn't go the way I may have wanted. Also, I think that these experiences (even though they may suck at times) are all learning curves, and what you learn from them helps you on the way towards what's meant to happen for you (if that makes sense?). In this way, everything that you go through contributes somehow to the bigger life picture.
I know this is way easier said than done, particularly when feelings are involved. But the way I see it, it evidently wasn't meant to be (sorry for how cheesy that sounds), and that's cool.
Peace yo xx