The third Lubavitcher Rebbe said that if people knew the power of tehillim we would never want to stop saying it.
I’m sure there’s a lot of sources on the power of Tehillim.
I also read a really inspiring article in Bina I think from the daughter’s perspective about a woman whose son was not successful in learning and who took on saying the entire sefer tehillim each week and her son slowly became more matzliach. What was especially inspiring was the effect this had on the daughter as well.
I think for me just knowing that Dovid haMelech went through so much and left this for us to turn to when we are in trouble or just to feel inspired. One Rosh Hashanah I tried to really slowly read the Tehillim and try to understand it more and that definitely helped a lot as well.