Hardest Lesson of life

when you go through the sad phase of life, we tend to learn many new philosophy( i mean to say hardest lesson) on the way. well, you must have read or heard this many times but i guess it suits to the context presently i am going through.
Life is all about letting it go, something which you desire the most, no matter how difficult it is. Initially it will hurt but later you get used to the pain i guess ( we tend to accept the things the way they are, not how we wanted it). If it comes back to you, it was yours. Else it was never meant to be yours. Yes that's the hardest thing but one need to accept it.
Like many say, you cant possess it( it here refers to the object of your desire) nor can you hold it tight in your hand cos its like the sand you try to hold in your hand, and when you tighten your fingers around it, it slips through, that's the way life is!