Tehillim, he can be assured that he said at least a little with kavanah.
Saying All of Tehillim Three Times in One Day:
It is said in the name of Rav Elimelech of Lizhensk zy”a that if a person recites the entire Sefer Tehillim three times in one day, it is more powerful than if he had fasted for an entire week, from Shabbos to Shabbos.
Furthermore, it is stated in Siddur Rav Shabsi (Segulas Hataanis) “If one wants to do teshuva but he is afraid that he won’t live long enough to fast enough days to atone for his sins, he should commit to hastening his teshuva by fasting from Shabbos to Shabbos, as this has the same value as 65,000 fasts.”
This would mean that according to Rav Elimelech’s words that saying Sefer Tehillim three times is more valuable than fasting from Shabbos to Shabbos, it comes out that reciting Sefer Tehillim three times is also more powerful and more effective for teshuva than 65,000 fasts.
Ziknei Torah are Those Who Say Tehillim:
The Mishnah (Kinim 3:6) states: “Ignorant old people, the older they become, the more their intellect gets befuddled, as it is said (Iyov 3:21): ‘He removes the speech of men of trust and takes away the sense of the elders.’ But when it comes to aged Torah scholars, it is not so. The older they get, the more their mind becomes composed, as it is said: ‘With aged men comes wisdom.’”
The Rebbe of Vilednik zy”a (Sefer Sheeris Yisroel, Shaar Hiskashrus, Drush 7) explains that “ignorant old people” (ziknei am ha’aretz) does not necessarily refer to people who are ignorant of Torah. Rather, even a person who knows all of Shas and Poskim is called an am ha’aretz if he is immersed in “artzius”, earthly desires. The Mishnah says that such people become more befuddled as they grow older.
“Elderly Torah scholars” (ziknei Torah), on the other hand, refers to those who learn properly, even if they aren’t knowledgeable in all of Torah. Even if one can only say Tehillim and sing praises to Hashem, he is given this lofty title if he does so with proper intentions.
Saving a Jewish Village Through the Power of Tehillim:
The Mahariyatz of Lubavitch zy”a related that the Baal Shem Tov zy”a once decreed that a Heavenly decree of destruction had been issued against a certain Jewish community. He sent for several hidden tzadikim and had them make a beis din to try to cancel the decree. He then made “aliyas neshama” and ascended on high, where he saw that the decree could not be annulled.
On his way back to this world, he saw that one Heavenly chamber was shining with a great light. It became known to him that this was the chamber of a simple villager who would recite Tehillim as he chopped wood. Even though he didn’t know the meaning of the words he was saying, he would recite the entire Sefer Tehillim five times every day. Therefore, the letters of the words of Tehillim were shining brightly in his chamber.
The Besht traveled to the home of that villager and told him, “Do you know that you have the ability to save an entire Jewish community? If you give over your reward in Olam Haba to them, they will be saved from destruction.”
The villager replied, “If I have Olam Haba, I am willing to give it to them.”
And the decree was canceled.
From this story, we see the great value of Tehillim. Even when one recites the words without knowing their meaning, the Tehillim is powerful enough to save an entire city from annihilation.
A Segulah for All Yeshuos:
It is said in the name of the Baal Shem Tov Hakadosh zy”a that reciting one chapter of Tehillim with emotion, doing an act of kindness for one Jew, and showing love for a Jew are the keys to the Gates of Divine mercy, and they are segulos for refuos and yeshuos.
Therefore, during the days of Shovavim one should strengthen his recitation of Tehillim. In this merit, one can accomplish great things.