Yep - and I'm probably not the only one. Although it it was usually asking myself "Did I take it or not?" and I found the NovoPen Echo to be really useful in this respect as it has a doohickey on the end that records the last dose administered and how many hours ago it was.
I'm on a pump now, but when I have forgotten a basal dose on MDI, I took about 2 thirds the following morning and corrected for the initial high. (And tested rather a lot).