Tactical engagement in multiple teams

I got an opportunity where I was working for two teams at the same time tactically , by tactic engagement I mean at the implementation level.

I have the following observations,

1. Focus is divided , although you might be able to split your time accordingly but I find it difficult to clear my thoughts from the current context to another context. Even though I was able to switch work accordingly but my brain was still stuck and thinking about the other context.
2. If I moved from one context A to context B , the context A is not static in nature and thus evolving all the time so the time I keep working on context B I miss the difference of work in context A from the time I switched to context A to the time I switched to context B again.
3. Because of the lack of focus , quality was suffering in one of the streams and I got into rush unconsciously of just get it done , but it was also not getting done because of lack of focus .
4. Because of lack of deliverables and late deliverables I got an impression that trust deficit was building as well.

This strategy was adopted because of lack of people and from what I understand it was an attempt to optimize on number of people.I am willing and open to listen how others are solving this problem ?

These opinions are my own and I not in anyway represent any entity in any form