What people said.
Mentally review the past two weeks, or longer if you can. Write down every compliment and every piece of positive feedback you got on your work. Yes, including the ones you brushed off with "oh, it was nothing."
What they wrote.
Go through your emails for positive comments, compliments and reviews of your work. Move every one of them into a new email folder called "Brag Sheet". Then log the best lines here so you have them in one place.
What you did.
Look back through your calendar for the past few months to remind yourself of all the meetings you had. For each one where you showed up well, write down when it was and what you did really well in it.