Mickey wished he could believe whatever was going on between Rose and the Doctor was just a fling, but seeing how she lit up whenever the Time Lord was around, he was pretty sure it wasn’t.
The Doctor had the same kind of look in Rose’s presence; everything he did seemed geared towards impressing her. It cut like a knife to Mickey’s heart. He wasn’t needed anymore, if he ever had been; he doubted they’d notice if he left.
He’d loved Rose for as long as he could remember, thought they’d grow old together. Instead, he was letting her go.