Solvitur ambulando
A Latin phrase meaning "it is solved by walking", often attributed to Augustine, but originating from an account by Simplicius of Cilicia about Diogenes and Zeno.
According to Simplicius of Cilicia, when Zeno was debating the existence of motion and his paradoxes, Diogenes replied by silently getting up and walking away, proving it is real.
Much like the idea that "Demons hate fresh air", when faced with mental difficulties, walking can help a great deal. It might not solve everything, but staying inside and staying in bed solves nothing.