My wonderful mum, who is no longer with us (it's six years this year and I still miss her everyday), always used to say to me:
"Everything happens for a reason", and used to qualify it with "you may not know why now, but it will all become apparent one day".
And from that I took great strength, particularly when my marriage ended, and when my father was gravely ill (but recovered), and when I lost my grandma and then very shortly afterwards my wonderful mum, both very unexpectedly. I think it has shaped the person I am today a great deal.
She also had a few others:
"If you can't say anything nice, don't say anything at all" (said to me a lot during my late teens lol!)... And...
"Don't do what you like - like what you do"
And one from me (which I read in a magazine article many years ago and which I hold to be true):
"People come in to your life for one of three reasons: a reason, a season or a lifetime".
This one has helped me not to dwell on ended relationships (whether male partners, female friends or colleagues), particularly if they met a need (whether for both of us, me, or for them).
And finally, one from my grandma:
"The way to a mans heart is through his stomach" 