||Shavuot 15B & TuSh"A Y"D #179
Tehillim is Pesukim of Tana"ch, it is not Tefilot (prayers) for you to say. There are Tefilot that we were given to say three times a day. Spend your energies working on them; understanding them, concentrating on what you are saying as you are saying it, and of course making sure that you are 100% following all the rules properly. If you are not, how can you expect to be listened to.
Sadly, I'm certain that many people who were sick got negative reactions from the Tehillim said, and from the "Mi Shebeirachs" said while the whole Shul is talking. A person who is sick should prefer not to be included in the average shul's "Mi Shebeirach."