"The people who questioned my decision to become an extronomer were right. I was wrong. It seems too late to get back in."
This mindset irks me because this individual strikes me as being bright, talented, curious, and hard working. You are not wrong because you took a leap in life and it didn't work out perfectly, its a valuable learning experience. It is different if you assess the opportunity costs and risks and rewards with going back to astrophysics and decide that it is not worth it and move on...but to say it is 'too late' is you pouting and trying to let yourself down easy.