I didn't leave mine to cry. Well, a little but if he cried in distress the noise went through me like an alert sounding the call of nuclear war.
A few things that helped:
A dummy. I was against it originally but I got PND from sleep deprivation so it was a case of needs must. It didn't cause any long term problems and I don't regret it now.
Loud white noise. Weirdly, the louder the better.
Warming the cot up a little with a hot water bottle on cold nights. Obviously taking it away before he went down.
I can't remember what they're called now, but those sleeping bags babies wear.
Sometimes some paracetamol. He couldn't tell me if he was in pain so if he was really unsettled, I'd give it anyway just in case he was teething or had something else niggling him.
Otherwise just co sleeping and feeding to sleep. Not my original intention but it was impossible to get any rest otherwise. Again, it caused no long term problems and he was sleeping entirely alone by the time he was a year old. No regrets there and I'd have planned to co sleep if I'd had another.