One way is to bundle an activity that you might not consider fun with one that is fun. For solopreneurs, that might be something like inviting a fellow solopreneur, or alternatively a friend that has the flexibility to work remotely and invite them to share their workday with you in a co-working space.
Another way to incorporate more fun is to reframe tasks that are not traditionally fun into something that you consider more fun. For instance, simply approaching a situation with the attitude “I am going to have fun with this” vs. “this really isn’t going to be fun” can make all the difference. With a fun mindset, you focus on and amplify the fun aspects of an experience. Conversely, when you approach a task believing it won’t be fun that mindset can become a self-fulfilling prophecy..