@iLED009 you are right. All our emotions are nothing more than some chemical reactions going on in our brain. And all human emotions are coping mechanism for survival encoded in our genes we acquired through millions of years of evolution. And modern medicine which treats/masks these emotions (anxiety, anger, depression etc) are also our way of expression of our survival instincts.
Now the million dollar question is Do you want to buy happiness ? The answer is YES, until it involves relationships. So lets say you went to a relationship therapist. And he gave you a prescription. If you give your partner one pill every morning, he/she will love you the way they did at the start of courtship (it should be possible.) Will you accept it ?
So in my opinion, the only answer is TO ACCEPT CHANGE than feel nostalgic. Open your eyes, mind, horizon and embrace life or just change the course.