  We propose a new approach to obtain the momentum expectation value of an
electron in a high-intensity laser, including multiple photon emissions and
loops. We find a recursive formula that allows us to obtain the
$\mathcal{O}(\alpha^n)$ term from $\mathcal{O}(\alpha^{n-1})$, which can also
be expressed as an integro-differential equation. In the classical limit we
obtain the solution to the Landau-Lifshitz equation to all orders. We show how
spin-dependent quantum radiation reaction can be obtained by resumming both the
energy expansion as well as the $\alpha$ expansion.
