The beauty of personal growth and career development is when your projects and assignments are harder than your current skillset. That is the formula, which I tested on my own skin and I don’t tolerate those environments that do not have or offer such incentives.
Only if you challenge yourself with more difficult tasks and continuously exit your comfort zone, you have a chance to become really exceptional. In my own example, I chase assignments to more and more complex projects, because they present a challenge, make me think and find creative solutions. That is all that matters.
Once you prove your ability to deliver, keep going – ask for more. Everyone had to do something for the first time, with failures and mistakes, then did it again but better, and then again – but more difficult. That is how it has to be.