The more frustrated, the braver.
If you don't advance, you will retreat. -Liang Qichao
Difficulties and setbacks may be beneficial. This is a kind of exercise, which is my motivation to move on. -Xian Xinghai
Only difficulties can make people show their true colors. -epiktetos
The most difficult time is the day not far from success. -Napoleon
Difficulties come, some people soar because of it, and some people can't afford to fall because of it. -Tolstoy