In order to prove that
$$\lim_{n\to\infty} a_n = L \implies \lim_{n\to\infty} |a_n| = |L|$$
I started with my assumption:
$\lim_{n\to\infty} a_n = L$ we have:
$$n>n_0\implies |a_n - L| < \epsilon $$
but I can say that $$||a_n|-|L||<|a_n -L| < \epsilon$$ rigth?
Then my proof is done?
Just a small technicality: you should write $||a_n| - |L|| \color{red}{\le} |a_n - L| < \epsilon$, for it may be the case that $a_n = L$ for some $n$.