I don't know if it's such a negative thought. I think it's better than "I am important", a thought which I associate with the sort of people who scream at the hotel staff for decorating a room with flowers of the wrong colour.

As long as you never go into "I'm less important than him/her", you're fine.

And remember: being unimportant means you have the scope to become important in whatever way you want. You have the freedom to carve your own way in your own way.

As long as you never give people hell over trivialities.