Vastu is proven to beneficial in restoring the family bonding and harmony. The source of eternal joy lies within you only, but due to external environmental factors, you are not able to feel the happiness.
According to me, it can be any one of the cases :
Case 1: You don't like your career. If u don't enjoy or love what you do, you will not be able to concentrate on your work because you don't like doing it. So try doing what you like and enjoy.
Case 2 : You like your career but you are very disturbed over something. You might be thinking about something that is bothering you a lot. You should over come that by either staying away from something which disturbs you or stay away from someone who is bothering you in your thoughts. If you don't like something just state your opinion in front of them. So you just spit out and you feel relieved.
Case 3 : If it's not any of the above cases. It might be lack of sleep and excercise too. Sleep well. Try out yoga or meditation. Drink lots and lots of water. This increases your concentration and keeps you energized throughout the day.