I was seriously scared about flying solo for a long time. I think it lasted about 20 years, and no I'm not exaggerating. Like you I would get really excited about an upcoming flight, but once the day got here all the things that could go wrong would start running through my head.
I'm not sure why I kept flying. Maybe because where I live is so beautiful from the air. Or because I liked the challenge. Or because I felt some need to face my fears. I'm still not sure.
At some point the fear began to ease and the last 10 years have been much better. I still get nervous but it's not the same kind of intense fear. I think it got better with my skill level and my knowledge.
I finished building my own plane 6 years ago, and for a while those fears came back (for good reason, I knew nothing about building an airplane). Now I have 600 hours in my plane and the fear is back to a reasonable level. Almost as if the word "fear" doesn't apply anymore. Nervous before a flight, yes. But not fear.
Might current perspective is due, in part, to the fact I know every inch of my airplane. I pull the cowl and inspect the firewall forward every 10 hours or so. I know there are no hidden gremlins in my plane that are going to bite me. I think it helps if you really take some time to look at, and understand, the internal workings of your plane. The engine, the controls, the gauges and accessories. This may not be easy to do if you don't own your own plane but you can research your model aircraft online and watch YouTube videos. Maybe next time the plane goes in for an annual ask the mechanic to give you a tour once everything is opened up.
Lastly, use the fear you have to fly safer. Climb higher, even on short trips. Be conservative on no-go decisions. Training has a tendency to focus on what can go wrong. So look for things that can go wrong before each flight and make a plan as to what you will do if it happens. Mentally run through each segment of the flight and have a plan for each problem. Having a plan in mind ahead of time helps keep me calm and focused.
30 years later and I occasionally still have days when I get to my hangar and start to get ready for a flight, and some little voice says "don't fly today". It's irrational, illogical, and has no basis on fact. Yet, when that annoying little voice, or intuition, speaks to me I lock up the hangar and go home. Is it fear? Maybe, I don't know.