Flu vaccines simply increase your immune system's reaction to particular variants of the flu virus. It doesn't mean you can't get the flu, but if you do your symptoms are likely to be milder than they otherwise would be (unless you happen to get a different variety of flu than the one the vaccine was targeted at).

Also, one single person's experiences with the flu vaccine are not much to go on when making conclusions about the effectiveness of the flu vaccine for millions or billions of people.

Just to provide a counterexample, my own experience has been that I used to never get the flu vaccine, and once got so sick with the flu that I thought I was going to die (later I learned that some people actually do die from the flu). Then I started getting the vaccine every year, and since then I mostly didn't get the flu, but in the years I did my symptoms have been relatively mild and short-lived -- it usually lasts a day, and I don't feel like I'm going to die; instead, I just get some weakness and muscle aches.

Another thing to consider is that there may be other reasons for getting sick or not, apart from your vaccination status. I used to have a poor diet and some nutrient deficiencies, but since I improved my diet and started taking supplements like vitamin D and B12, I very rarely get sick. I think my immune system is probably just generally stronger than it used to be.

So to really make solid conclusions about the effectiveness of flu vaccines, you not only have to study large groups of people, but you also have to control for all the other factors that could potentially influence how frequently and how severely people get sick from the flu.