Leonard: “I don’t even know how long she’s been gone… It’s like I’ve woken up in bed, and she’s not here because she’s gone to the bathroom, or something, but somehow, I just– I just know– she’s never going to come back to bed. If I could just reach over and touch her side of the bed, I would know that it was cold. But I can’t. I know I can’t have her back, but I don’t want to wake up in the morning, thinking she’s still here.”
…
“I lie here not knowing how long I’ve been alone. So how: how can I heal? How am I supposed to heal, if I can’t feel time?” ^†

^† — Memento, the film. (dialogue, at approx 00:38:00).