A person does not only have to hold onto hope to get out of their situation. Hope can be the key to survival, but just hoping won't do anything. Maybe a little more effort into getting out of despair will work, but clinging on hope will help less.
When things have gone awry, to the point of no return, survival kicks in. This need to survive is based on hope: believing that you can overcome this obstacle, or navigate the turmoil that life throws at you. Hope is also the basis of of inspiration to overcome this obstacle. Hope and survival are essentially the driving forces of your actions when your in trouble. If you don't have any hope and desire to survive, you essentially admit defeat and get nothing done. The only idea that a person needs to hold onto is hope when in trouble. This doesn't necessarily mean remaining stagnant in your progress of overcoming your obstacle and hoping that something will happen, because hope is the driving force of survival in the first place. The statement doesn't say the only thing you can do is hope. It says the only thing you can hold onto is the idea of hope. Holding onto any other contradicting idea (doubt) can result in not overcoming your obstacle.