A friend once said every now and then you have to try and lift a weight that scares you.
This was good advice. 
I’ve always been a conservative sort of lifter. I keep my weights manageable, rarely ever working to failure. I save the gut-busting sets for bodyweight exercises where there’s less risk of suffering something catastrophic. I consider this to be a sound approach to resistance training, however there is a serious flaw that needs to be called out: unless you work to failure, how do you know what failure feels like?
If you’re doing things right, strength gains should go up over time. Todays 5 rep max could be next month’s warm-up set. This is why it’s important to check in with those aforementioned scary weights every so often, to recalibrate your idea of what heavy is.
Here’s a good method for ensuring you’re not short-changing yourself: for rep schemes greater than 3, by the half-way point you should start to hear that nagging voice of doubt in your big dumb brain. If you hear it after 1 rep, you’re going too heavy. If you don’t hear it at all? Consider that a warm-up set. Add more weight and do it again.
Lifting weights isn’t supposed to be hell.
It ain’t supposed to be easy either.