I find things to be grateful -- things得去感恩别人，逻辑上乱成一团

I find things to be grateful for-- 你感恩你发现的things，逻辑正常。

形容词不定式可以等于关系代词作主语所引导的定语从句

I have no friend to advise= I have no friend who can advise me.

There is one thing to be done= there is one thing which should be done.

很明显网友的句子不是这种用法。

应该是下面的用法，形容词不定式也可以等于关系代词作宾语所引导的定语从句

I want something to eat= I want something which I can eat.

which作eat 的宾语。

,the more you will find things to be grateful for in your life.=,the more you will find things which you should be grateful for  in your life.

which做介词for的宾语

 grateful for: I’m very grateful for all your help with the party.

这是grateful的用法