There is lots of food for thought in the responses here. Timber has drawn my blood several times. I totally understand your feelings of hurt because I have felt the same. As you said yourself, your circumstances and where you are at emotionally right now magnify that.
Timber is a "spite biter." In other words, when he doesn't get his way or is angry at me, he is likely to bite. No warning, no heads up, just bam. The second time it happened, I remembered posts I read on here saying that greys are emotionally at the 2-year old toddler level and they stay there. When they are frustrated and upset with us over some real or assumed slight, what recourse do they have? They bite. That is the way it seems to me at any rate.
There may be any many other factors that influence it, including hormones and things going on in their birdy brains they we don't know or have a chance of comprehending. I just keep trying to figure out how to prevent it and when to expect it. When dealing with the hurt, I always remind myself that Timber is not a human. He doesn't think and feel like I do, nor does his behavior follow human patterns and expectations. Because our birds are smart and can reason, I think we sometimes attribute human feeling and responses to them. I remind myself that Timber has no idea how much a blood drawing bite hurts me physically or emotionally.
Hang in there!