The use of "yo"

I see that “yo” is used a lot in sentences like “Cuando yo era niño, no tenía una computadora.”

In all my previous lessons I have never seen this, and I have always been taught to use “yo” sparingly and only for emphasis. I do see  “yo” used when learning conjugations, such as “yo era”, tu eras", el era"…etc. But it seems unatural in conversation. Am I off track thinking this?

Thaks, all of your comments always appreciated.

I think I've learned that Yo is used sparingly. I wrote a little paragraph for my tutor with “yo this” and “Yo that” and she said people will think I'm egotistical if I overuse it. 

What I've learned is that the personal pronouns are often used for emphasis.

But I'd assume that the native speakers who put together Rocket Spanish know how to speak their language and are putting together the lessons with a mixture of usages.

And I'm learning more and more as I learn to not sweat the small stuff.

¡Hola BarryH12 y Daryl-O1!

You're both right to say that personal pronouns like yo are usually used sparingly in Spanish: most of the time, speakers drop them unless they want to show emphasis or to clarify who they are talking about. 

So it's possible that you'll find native speakers including yo in sentences that begin with Cuando yo era niño / niña because they're subtly emphasizing their own experience - a bit like saying “Well, when I was a kid, things were different" in English. But in conversations like the one in Lesson 9.3, the added pronoun can be necessary for clarity. 

This is because in the imperfect tense, the verb ser “to be (permanent states)” conjugates in the same way for yo and for él / ella / usted: it takes the form era. And in the conversation in Lesson 9.3, we actually have a number of people involved: the narrator Amy is present, and she says that Mauricio is telling you, the listener, about his mom, Carmen, and how she used to always tell him about her own experiences growing up. As a result, if (for example) Carmen were to start her sentence with Cuando era niña, it would be ambiguous: it could too easily be understood as “When (she) was (a) girl” (talking about Amy) instead of as “When (I) was (a) girl.” So, Carmen adds the subject pronoun yo to make everything crystal clear. 

In the Lesson Vocabulary section, you'll find sentences both with yo and without, to help you practice using the emphasized/clarified version of the sentence and using the ordinary version.

I hope that this helps to clarify everything. Let me know if you still have questions!

Saludos,

Liss