Adding line break in esc_html__

This is just one way of doing it using sprintf

echo "<span class="gp-success">" . sprintf(esc_html__('We have just sent you an email with instructions to reset your password.%sIf you do not receive a reset email or password email please look in your spam folder.', 'socialize'), '<br>') . "</span>";

Notice the %s in the string, this is a “placeholder” for the second and later arguments that are being passed to sprintf.

A side note, in php its better to use ' instead of " for pure strings, " also checked the string for variables and thus costs more resources, when you can, if you only want to output a string, use '.