您提供的句子确实有点含混不清。更清晰的表达似乎应该是这样的：

When you feel tension building, find something fun to do. You'll find that the stress you feel will dissipate and your thoughts will become clearer.（that为宾从，the stress为宾从主语）

当你感觉到紧张的压力，做一些有乐趣的事吧。你会发现压力在渐渐消逝，你的想法也会渐渐明朗起来。