Design like a detective
One of the first obstacles a new designer needs to overcome is the fear of failure. The way to overcome this is to constantly remind yourself that you're in the business of solving problems. Anything that brings you closer to solving the problem is good. Anything that leads you in the other direction is bad. And as Thomas Edison famously said:
I have not failed. I've just found 10,000 ways that won't work.
When a design I created universally fares poorly in user testing, I'm thrilled. Before testing, every design decision is a hypothesis. Experience and wisdom will help you come up with better hypotheses, but no amount of experience can guarantee the right solution. A universally hated design is a neon sign pointing you in a better direction. You don't get those signs while seated at your computer tinkering with different layouts and interactions. That's just the process of fine tuning your hypothesis.
You will go through several levels of maturity as you grow in your design career. At first, you'll hate being wrong. Eventually, you'll learn to accept and tolerate it. And finally, the day will come when you learn to love it.
Always remember that as a designer it is not your job to create the best solution, it's your job to find it. Sometimes, you'll create a new whiz-bang UI that solves your client's problem. Sometimes, someone else will propose an idea that solves it. At which point, it's your responsibility to humbly accept that fact and do your best to fine tune and shepherd that idea through implementation.
Design is like a detective story. No detective ever solves the case immediately, on their own, with no help from others – or without making mistakes. The evidence may lead them to countless dead-ends, but the best detectives are undeterred – and even energized – by these setbacks. Approach new design challenges like a detective and you'll ultimately have more satisfied clients and users, and you'll even have more fun along the way.