Davening with kavanah is difficult for most people, and this causes many to disregard and disrespect their tefillos. They think, "What value can my tefillos have? They were mumbled without kavanah!" But every tefillah is exceptional, including those said without kavanah.
The Torah (32:9) tells us, ויחץ את העם אשר אתו... לשני מחנות, ויאמר אם יבוא עשו אל המחנה האחת והכהו והיה המחנה הנשאר לפליטה "He divided the people who were with him...into two camps. He said, 'If Eisav comes to one camp and strikes it down, then the remaining camp shall survive.'"
The Chozeh of Lublin zt'l explains that Eisav is the yetzer hara, and the two camps are the heart and speech. The pasuk is saying that if the yetzer hara smites the heart, and one cannot daven with kavanah, at least salvage the other camp, which is your speech. Say the words of the tefillah, even without kavanah, because those tefillos will also be answered.
The same is said regarding Tehillim. Tzaddikim have said that one should say Tehillim, even without kavanah, because just by saying the words, one brings about salvation and blessings.
Reb Chaim Brim zt'l brought a beautiful source that tefillos, even without kavanah, are effective:
If someone says ותן טל ומטר in the summer, he must repeat the Shemonah Esrei because, in Eretz Yisrael, rain is a curse during the summer. This halachah applies even if he said ותן טל ומטר without kavanah.
How much influence can his words have? He probably has no idea what he said! Yet, it is considered a curse, and he must daven again. We see that all tefillos, including those said without kavanah, accomplish so much!
Obviously, if he can daven with kavanah, the tefillos will be far greater, but let us be aware that every good deed, even tefillah without kavanah, is cherished and accomplishes a lot.
Tehillim קי"ט
Tikunei Shabbos teaches that reciting chapter (Tehillim 119) קי"ט banishes the kelipos. Included in "kelipos" are our enemies and the yetzer hara. It is therefore very beneficial to recite this chapter. Some say it every day.
It states (Devarim 6:19), להדף את כל אויבך מפניך, "to thrust away all your enemies from before you."
How do you thrust away your enemies? The Or Pnei Moshe (Va'eschanan ד"ה איתא בתקוני שבת) says that this is done by reciting chapter קי"ט of Tehillim. להדף is gematriya 119, and ת"א is roshei teivos for תמניא אפי, which means "eight phases," alluding to chapter קי"ט of Tehillim, which is called תמניא אפי because it contains eight pasukim for each letter.
The Or Pnei Moshe writes, "When one says this chapter often, it causes להד"ף כל ת"א אויבך, the enemies within us to become shattered and removed."
The Imrei Noam (אות ט"ז או יאמר) writes that before Yaakov Avinu met with Eisav, he said this chapter for protection. A hint is וישלח יעקב מלאכים לפניו, and לפניו is gematriya 176, and there are 176 pesukim in chapter קי"ט of Tehillim. The chapter begins with אשרי תמימי דרך, and Yaakov is called איש תם, as it states (Bereishis 25:27), ויעקב איש תם יושב אהלים.
When Yaakov wrestled with Eisav's malach, it states, ויאבק איש עמו, "a man wrestled with him," and ויאבק is gematriya 119. These are all remozim, hints, that this chapter helped Yaakov overcome Eisav.
As we wrote, some people say this chapter every day. If it is hard to say it every day, it would be a good idea to say it at least once a month. It banishes all enemies, the enemies outside us, and the enemy within us, the yetzer hara.