Every occupation has its risks and hazards that could potentially result in workers suffering injuries. In your case, you may work in construction and face the possibility of falling from a considerable height, having a structure collapse on top of you, suffering injuries due to equipment malfunction or any number of other serious scenarios that could easily result in your harm. Unfortunately, it only takes one accident to leave you with permanent injuries.
Receiving notification that your workers' compensation claim was denied is both shocking and discouraging. Typically, when a claim is denied it's because the insurance company decided that your injury does not meet the necessary standards and therefore shouldn't be covered by workers' compensation. This is upsetting because you know in your heart that your injury was legitimately sustained at work and you don't understand how they could disagree.