The vice of procrastination
We probably would all do well to tack on somewhere prominent this footnote from the novel Jonathan Strange and Mr Norrell the soonest we find time:

Horace Tott spent an uneventful life in Cheshire always intending to write a large book on English magic, but never quite beginning. And so he died at seventy-four, still imagining he might begin next week, or perhaps the week after that.