It doesn't really matter if you're writing a novel, a magazine article, a cartoon strip or poetry. It's easier to write about something you know than what you don't know anything about. If you've spent your life working in education, writing about students, parents, teachers and homework should come easier than if you've spent years working in construction.
As I write and submit cartoon gags, thousands of them, I often ask myself what should I be writing about? What should I be focusing on? What's easy for me? For the cartoonist or gagwriter, if you can find the subject you know and have opinions about, it'll be a lot easier for you to succeed. I spent many years working in offices, so I can relate to the whole boss/worker situation. I know about job interviews, having gone on many of them over the years. I know about salary issues, co-worker issues and all the other crazy things that go on in offices. I write a lot of business gags and they seem to come easy to me.
I also write for the syndicated strip, The Lockhorns. This very long-running strip shows, with great humor, the conflict between husband, wife and wife's mother, with a marriage counselor, friends, doctors and shopkeepers added to the mix. The thing is, I can identify with this couple, drawing from my own experience, my husband's, my father's, the fact that I now am a mother-in-law, etc. Some of these issues are: my lack of cooking ability, my tendency to spend money, my tendency to not spend money, to not have enough money, laziness, family issues, etc. There's plenty of material I can find right around my house. It's easy for me because I can relate to it.
I guess if you're thinking about creating a cartoon strip or just submitting cartoons to various publications, you should ask yourself what's easy for you to write about, what opinions do you have, what's funny about your life. It will be much easier to write about these things for the long haul than to write about something you know nothing about. You have to be honest about it, but once you find what you should be writing about it gets much easier.