Even if you're mixing yourself, it's better to add EQ and compression only when you can hear how it will sit with the soundtrack or special effects. Ultimately, it comes down to knowing what your voice will be used for and making a judgement. For instance, if I'm recording a tagline for a TV or radio advert, I'll generally run a mic into a nice preamp (where I might add slight tube warmth, and subtle EQ or compression, just to give the recording a bit of 'body'), and I may do a little de‑essing using a plug‑in when performing any edits. However, for e‑learning jobs, corporate videos and so on, I'll tend not to add any creative processing while recording or editing, and will only use the de‑esser ever so slightly.
In late 2009, my wife Simone received an email from Prague in the Czech Republic. The sender, Mirek Jirku, was heading up a project to record voice messages for the foreign‑language versions of the latest Avast! anti‑virus software. Mirek sent us eight messages to be recorded, specified the fee and deadline, and requested a slow, friendly read. He asked us to send separate stereo MP3 files (at 160kbps or higher quality) for each message, specified that we'd have to sign a non‑disclosure agreement before recording, that we'd need to invoice afterwards, and that he'd pay via a wire transfer instead of PayPal (which is often used for international payments).