In job interviews, I've always had a good answer when asked what my biggest working flaw is: I'm a poor delegator. When working on something, my instinct is to do everything myself, and it's not at all natural for me to have other people help.
In the few times I've been in a genuinely managerial position, that has had benefits and disadvantages, because when I do hand something off, I tend to hand it off totally, letting the person responsible work freely. But that also means I may not follow up as much as I need to, or won't delegate when I should really find someone with better expertise than mine. Generally, my lone-wolf tendencies worked great when I was a freelance editor, since my clients expected me to work alone—and often frowned upon any sort of subcontracting. But my current permanent job is not so clear-cut.
This week offered a good example of my previous working-for-myself approach. An old freelance client offered me a contract, but my schedule didn't allow me to do it, so I helped find others who could take the job instead. I was surprised at how many took it on as a team project, with different people planning on doing editing and photography work, for instance. When I did this same job two years in a row a few years ago, it never even occurred to me that I could recruit someone to help. Of course I'd do it all (and make all the money!) myself.
Likely this all stems from my being an only child, something I never regretted or resented, but something that has made me tend to go it alone. Still, I should learn to share my work more. It would sometimes get done better if I was a bit less of a hog—or a wolf—about it.