When I work on side projects or projects that do not have any other peers in my team, I find it extremely hard on the long term to keep working in the same way as I would do as part of a group of peers. With nobody looking at the same code, it promotes taking shortcuts.
"I don't need to loose-couple this because it will go away anyway", or "I know why I'm doing this" are all statements that I've come to regret one way or the other.
I think for me personally, it's okay if I can pretend that I have peers around me. Put a pull request in, do a code review on my own code, to make sure I keep tabs on myself. Holding myself accountable for my own implementations.
It's hard, but it definitely pays off.