In the early stages, an employee or a co-founder is fully committed. The source of the commitment could be temporary enthusiasm. And I believe enthusiasm is a emotion, and all emotions are just temporary.
Except from equity and enthusiasm, how can you make an employee or a co-founder to stay fully committed to the project/startup? The reason I ask this question is because in a scenario when the co-founder/employee becomes enthusiastic about another project then I will lose their commitments to my project/startup.