To reach 1st jhana, do we have to let go, or do we have to put some effort?

Recently, I've been reading a lot about the different methods and perspectives for reaching the jhanas. For a long time, the only method I've been using is to "let go" everything, and to use the breath as a kind of anchor for the eventual and sporadic distraction. But I never felt anything like joy or rapture. A few days ago, I found a meditation instruction where the instructor tells that effort and will can be used to give rise to joy and to expand it throughout the body. An as soon as I started doing that, I felt and important qualitative difference in the kind of feelings arising. Is this application of effort compatible with "letting go"? What do the suttas tell us about this? Kind regards!