We need to be connected to the process of teaching, other teachers and to the students we teach. PD provides us that opportunity.
We should be engaging in collaboration with all our 'stakeholders' including teachers, parents, students, and community members and learn as much as we can from all of them. We need to care about the stakeholders to develop instruction and teaching practices.
If you are questioning your direction or impact, why not ask your students directly -- 'What makes a good teacher?' 'How do you like to learn new things?' etc. We can take the answers to help us guide our own teaching, but also to determine how to create responsive PD, too.
Collaboration might look like having a co-teacher or mentor that you check in with on a regular basis. I know that we do that when we are beginning teachers, but I think it helps to 'run things by' someone you respect. Collaborative tools and lessons or a short video or Skype at the end of the week (or whatever timeframe works for you) could help keep you energized. I know as a Librarian, I frequently feel like I'm on my own.