When you say Tehillim, it is as if and as great as Dovid Hamelech himself, saying them.

Dovid Hamelech wrote the Tehillim with Divine Inspiration – the Holy Breath.  This Holy Breath is still in the words of the Tehillim.

When you recite Tehillim, your own breath arouses the Holy Breath in these words.  Therefore, when you say the Tehillim, it is as if Dovid Hamelech himself is chanting them.  

~ R’ Nachman of Breslov zt”l

Something to Consider: People have reported reciting the entire Tehillim each day of Rosh Hashanah and experiencing incredible salvation in the year ahead.