You know your brand, but you are not your customer.
And therefore, it makes sense to hire a professional who can use their ‘expertise’ to make informed decisions for your brand based on success from past projects.
Engaging a professional with ‘passion’ is equally as important because it gives you a powerful edge to keep one step ahead of your competitors (as reported by Forbes here).
Because unless you have the expertise/passion you’ll be closer to ‘guessing’ the solution than ‘knowing’ it.
Takeaway: It makes sense to engage a professional with expertise and passion because your brand succeeds when it does – as explained here by Dan Schawbel of the Personal Branding Blog.