THE BEST MUSIC IS WRITTEN WITH A TEAM!
I get in the studio with a lot of various musicians (hip-hop and pop mostly) and always suggest an extremely collaborative approach to writing a song. Many musicians who don't spend a lot of time in the studio don't often write music collaboratively and aren't used to the experience. Writing a song with the band or producers in the studio and 2-3 songwriters or friends to toss ideas around with makes for amazing music, and an amazing good time! Let go of your individual expectations as a musician and flow with the team. Professionals at the top level collaborate in this way and you need to be able to create great music with other artists when the studio opportunity arises. Music and opportunity moves quick in this industry and you need to constantly be in the studio or practicing your craft in other ways. When opportunity comes you need to strike!
Having some material ready like a hook you love to sing or a verse you love to rap ready is always good, but don't let old ideas stifle your creativity. There needs to be a balance and I always encourage artists I work with to write a new song on the spot in studio sessions. Catch that vibe! Practice singing new rhythms and free-styling verses so that your creativity muscle gets strong.
Most Importantly - If you write music ACTUALLY GET IN THE STUDIO AND RECORD IT! Nothing will get in the way of future creativity more than having a million half written songs that are clogging the creativity pipes. Get out there and start creating. Is music your dream? Whats your dream? How are you going to get out there and achieve it?
Let's do this.