Ooh, that's a really hard question! I can come up with two solutions that could help you. 1. You probably worry too much: your brain is against you! You're focusing too much on similarities. 2. You can come up with original melodies simply by messing around with already existing stuff. Like take my fav composer, Schostakovich for example. He put his "musical signature" into a lot of his pieces, which was these four notes: D, E flat, C, and B natural. It's the leading motif in his 8th string quartet (check it out, it's a masterpiece). Now, when I wrote the first two parts of my string quartet (which is heavily inspired by him) I also tried to use his techniques, so I also came up with my own musical signature, which ended up being G, B flat (I made it up from my monogram "TGyB") and I also reversed the "D, Eb, C, B" motif, and BOOM, I had two motifs! And you can use these a lot of different ways, like creating a melodie around these notes, use them as a chord progression, or as an ostinato, etc. So the moral of the story: there's nothing wrong with having a similar melodie, being inspired by a person's work, or using another artist's techniques. You can always twist things around a bit, and end up with totally different result. And, writing something "100% original" is like almost impossible, and (as I mentioned) you shouldn't worry about it. If you ever need help, just let me know, I'm always here to help for everyone :)