As you will come to see, knowing that mental health is always available and knowing to trust it allow us to slow down to the moment and live life happily

你会逐渐明白，了解心理健康一直存在且可以信任使我们能放慢节奏、享受当下、幸福生活。

各位老师，请问本句中knowing的主语是什么？

slow down to 中，down是副词，这好理解，那为什么多一个to？