Assuming you have any remaining mental capacity to formulate thoughts....what do you think of?
I know others have said it helps them to think of other parents being awake at the same time but that's never worked for me.
For me, (having had a very sickly DS before DD) I often try and be grateful that I'm just feeding her and then putting her back down and not having to give calpol/pace around etc.
Also barf I sometimes stroke her head whilst feeding and try and think that these are precious times together as she will probably be my last baby, sob especially as she is going to kill me soon through sleep deprivation