If you're getting stronger and building bigger muscles then you need to use heavy weights. But increasing your weights can mean you don't always fully fatigue the muscles you're trying to. Why is this?
...Because your grip lets you down
Take dead lifting for example, it's a classic mass builder. Your aim is to lift heavy to build more muscle, but be warned, this won't happen if you can't hold on to the bar long enough
However there is a simple solution to the problem... weight lifting straps.
Weight lifting straps are easy to use, help to support the wrists and take most of the work off your forearms plus they can help to prevent rough skin and calluses.