It sounds like a simple case of nerves, although I wasn't so much nervous as excited on my first solo. Like you I learnt to fly (30 years ago) to overcome a fear of flying and it certainly worked for me.
Much later in life I started having "panic attacks" at home or in the car. These are quite frightening things and can happen to anyone at any time of life for no apparent reason.
Although I haven't had one for about 5 years, it stopped me flying (my own decision) as a P. Attack in flight as a single pilot is not something I would recommend to anyone.
Probably not relevant but thought I'd get that off my chest...