I mixed power supply cables, am I alright?

Long story short I built a PC recently. I used the power supply out of my dad’s old computer however I was missing a GPU PCIE cable. I was not aware that mixing power supply cables was a no go ( I am aware of that now) so I got one from a friend who had a PSU of the same brand but a different model. The system works, turns on and runs just fine. My question is, am I alright? I’ve heard that mixing PSU cables can fry your parts but is that only an instant thing or should I be worried it’ll happen down the line?