Is everything. It sounds cliché, but it really is.
If your mindset sucks, so will your business. It's simple.
And if you truly want to create and run a successful & profitable design business, you must first believe that you can and will. So if you've been seriously wasting time & energy doubting yourself and comparing your achievements to other designers you see online or social media, it's time for a major mindset check. Let's work this out together.