“If you love something set it free. If it comes back it’s yours. If not, it was never meant to be.” - Anonymous
It's a very interesting saying because the interpretation is that you're going to let fate determine the outcome of an event or situation; if you let it go and it comes back, it was because that was just meant to happen. If you're not deterministic this isn't your truth.
“If you love something, you have to protect it.” - Anonymous
Contrary to setting it free, this would suggest you should fight for what you love, to do what you can to protect it and keep it near and dear. This is much harder than letting something go because it's more involved and you're taking control of your destiny, so, you would feel somewhat responsible for the outcome (even if there was nothing you could do).
So, which is the correct train of thought? They are both correct. People are different; different experiences, different expectations, different realities. One persons truth of the world will be different from another persons. The only thing you can do is acknowledge the loss has happened and decide what you want or need to do, but whatever it is believe it's the right decision - you're not wrong and nobody should claim that you are. Look at the circumstances and see if you can compromise; humans want to live in a black and white reality but the truth is it's a monochromatic world full of different shades of grey; rarely are things presented in inky black or fluffy cloud white. Why did the loss happen? What could you have done differently? Was there anything you even could do? Sometimes we don't have control, and when that happens take the deterministic outlook, don't beat yourself up.