Songwriter Jason Sellers is still riding high from the success of his previous No. 1 hit as a songwriter, Jason Aldean’s ‘Don’t You Wanna Stay,’ which topped the country singles chart for three weeks. He is now only a few slots shy of No. 1 again -- this time with the latest Rascal Flatts hit, ‘I Won’t Let Go,’ which he co-wrote with Steve Robson.

“This was the first song Steve and I ever wrote together,” Sellers tells Taste of Country. “Steve is from England. He comes over from time to time. He is an incredible writer. He co-wrote 'What Hurts the Most' and some other hits. He had started this piano kind of arrangement thing, and we got together and worked on the melody. We really didn’t have to spend that much time on it because he had the musical piece already working. Then he went back and started building the [song’s] track, while I worked on the part. It felt so inspired. I wanted to make the message matter.”

I will stand by you / I will help you through / When you’ve done all you can do / If you can’t cope / I will dry your eyes / I will fight your fight / I will hold you tight / And I wont let go,” Flatts sing in the song’s chorus.

“It felt like a message that would be able to hit home with a lot of people,” Sellers says. “Flatts cut it, and here we are at No. 4 this week! I hope it will do somehow close to what [‘Don’t You Wanna Stay’] has done.”

Sellers also has another song burning up the charts right now ... Thompson Square's 'I Got You,' which proves that sometimes the Nashville stars are actually behind the scenes!

Watch Rascal Flatts Perform 'I Won't Let Go' on 'Letterman'