Luck or Work?

Right from the childhood I used to believe in LUCK. If a person achieves some goal in life its only because of his good luck and if he fails luck is against him. In one way or the other LUCK has a very crucial role to play. But (with a capital 'B') is there anything called LUCK really exists? or it is just a state of human thinking. Is this luck riding a person or is ridden by a person? Is luck biggest Weapon (Strength) of a human being or is the utmost Weakness? Is it luck by which a person hides his disabilities?
Some of the instances, that I could recall, am putting in this post:

It was my High School (10th std) Biology Practical Exam. On the way to my school a cat crossed my way (according to Hindu superstition it is considered very unlucky). Still I didn't stop and went on my way. The practical was good and I was very happy after practical. Results came and I got 17/20 in biology practical. Almost 99% of of students got 18/20 (may be general marking). Moreover I got 74/100. Had I got 18 in biology practical (as everyone got) I would have got distinction in one more subject (Biology). Should I blame my luck (because the cat crossed my way). Was it my bad luck or was there some scope left in my preparation for practical exam?

My college days, desire to achieve a lot in those 4 years. One desire included to be a topper for at least one semester. It was my 3rd year (most important year in engineering) and I was on verge of my studies. My little ambition of becoming a topper still was bubbling in my mind. Exams of 6th semester were over and we were waiting for results and finally my little desire was fulfilled. Should I say my Luck was shining like a star or was it my hard work that was paying off?

Final year of my college. Everyone was ready for Placement (every engineer's dream day) and we got news only one company is visiting that year (thanks to year 2002, IT was on its peak, but which side) for placement. Written tests were over and everyone waiting for the result. Finally someone came with a piece of paper with 7 names on list. I was pretty sure to be on the list. But what happened... where is my name in the list? Oh!! my God. My written test didn't go well or what? 7 toppers were on the list.. but wait I am also in list of 7 toppers, so why name is not there.. Oh no, I filled my marks incorrectly in the sheet provided by them and I came down to 8th position. Was it my mistake because of which my dream collapsed in one minute (or one second for that matter) or was it my Bad Luck because of which I filled incorrect marks or was it Good Luck of those guys who came above me because of my silly mistake.

At each moment, each activity, each difficulty, each exam, each result, I see Luck taking its part.
Whenever I think I find only one thing, If you work sincerely, with utmost honesty then Luck will always be in your favor and if there is any scope of improvement then you do not have any option left other than blaming you Luck.
Its only Karma (Work) by which you can control your Bhagya (Luck).

But wait a minute.. what if a person who worked very hard with full honesty and put his 100% in getting a Visa and he was refused only because of the bloody lucky draw concept.
What is a person was very sincere with his work throughout his life and at the time of promotion he is refused for it only because the manager's relative (though not a good team member) is promoted by manager.
What if a player (cyclist for example) was preparing himself for olympic and was the best contender and on the D day a car hits him and he lost his legs in that accident.
Its only Bhagya (Luck) that decides Karma (Work).

There are endless examples that can be given for these two statements. Person revolves around these two statements and is never in a situation to decide which statement is correct (at least I am not).
If you have any idea please do write your comments...