Let $\|\cdot\|$ be a norm on $\mathbb{R}^n$. Prove that there is a constant $C>0$ such that the entries of every $\mathbf{v}=\left(v_1, v_2, \ldots, v_n\right)^T \in \mathbb{R}^n$ are all bounded, in absolute value, by $\left|v_i\right| \leq C\|\mathbf{v}\|$.