If you are still unsure if your mix is ready for mastering, send it to the mastering engineer and ask their opinion. Any professional engineer will be able to help you catch potential issues in your sound and give you advice on how to address them within your mix to ensure best possible final results for your mastered song.
If you’re a part-time musician, you know the struggle. You want to make music, but you run out of time in a day. Or you lose heart. Or your music time is not as efficient as you want it to be. Every day, it’s an uphill battle of sticking with it, being productive, and not losing your mind.