Solve hard problems, do not run away from them.
Solving a hard problem increases your problem solving capacity, allowing you to tackle new problems faster and better.
The more you solve problems, the better you become. Problem solving is a skill, and with all skills whether it be cooking, programming, teaching or washing, you get better with practise.
This is why it is a great thing to always seek new challenges, without new challenges, your tasks become mundane. No surprises, no learning.
Step out of your box
Try a new challenge, look for a new problem to attempt, its all for greater good.