Meaning to "go hard", to toughen up over time and not be easily broken or consumed by anything. To do something to the best of your ability despite the circumstances.
Man, I had a long day and I'm tired but I'm still about to go up in this gym and go cold-biscuits on these weights.
Just because your girl dumped you, you stopped working out? Man you better keep it cold-biscuits and go hit the iron!