I found the agent-seeking process absolutely exhausting. After sending out 74 of them (all personalized, as you mention here), and getting virtually nowhere, I decided to self-publish. Granted, my novel will be seen by like 12 people now, but it was also rewarding to see the thing in print and to be able to have a sense of closure about it as I move on to the next one. Good on ya for going well beyond where I gave up on this goal!