Yes. This exactly.

Usually this question arises from people who care about other people in their lives. Maybe you think you're taking away something from someone else? Time? Concern? Attention? Maybe you think this is something you shouldn't be spending money on because— that money should be spent on other 'more important things, or people?

The oxygen mask metaphor fits very well for the first concern. You have to help yourself if you're going to be able to help or work with others. You may not think of it as "helping" but think of it as not taking your pain and suffering out on others. If we don't strive to understand the root of our own pain, confusions, emotional distress, etc. we let those emotions and issue take control without knowing. If you have a struggle in your life and your recognize that, you need to work on it with a professional in order to keep it from seeping out and leaking onto other people in your life that you care about.

That being said, therapy is for and about YOU and there's absolutely NOTHING wrong with that fact.

A responsible adult is a self-aware and self-cared for adult. Period.