If you want to be mentally strong, stop stewing on negative thoughts and feelings. Think positive.

如果你想坚强，就不要纠结于负面的想法和感受。要积极乐观地考虑问题。

youdao

After that I might only be able to play games here and there, who knows, but I think I can be an influence and be positive and win games and be strong for two years.

打从心底里我觉得我还能以良好的状态打两年，而这段时间内我的发挥也将左右许多东西。

youdao

So our oldest daughter said to him, daddy, I must say, you know, you always tell us to be strong, you know, and be positive and, you know, think of good thoughts and be thankful for what we have already.

NPR: Justine Simmons of 'Run's House' Pens Book for Kids