It doesn't automatically make a change in you by meditating for x amount of minutes/hours every day. It is akin to working out without having a healthy diet and wondering why you're not seeing any results after a year of exercising. You need to know what you want to get out of it, and when you do, meditating is 10 times easier, and 10 times more effective, because you know what results it is you actually want to get out of it. Otherwise it is very sensible to get lost in thought because you don't know what you're wanting to get out of it, so you expect too much from the simple act of meditating, making you lose focus on the task at hand and building up frustration that really shouldn't be there in the first place.

To use another analogy, it is like driving a car without knowing your destination and wondering why you're never getting there. You are in fact driving a car, so why are you never getting there.

I tipped about this in another reply, but I'll fire it here as well just in case, I believe your end goal is mindfulness, so I'd suggest checking out other people who speak about it so you get a greater sense of what that state of mind is. It is not something spectacular, it is just a great mindset that you can use as a tool to prime yourself whenever you feel a negative set of emotions - and even positive, to keep you present and not relying on certain said events to keep you happy - but instead find fulfillment in just the every day moment.

Once you have this, and you practice it through meditation, it'll get easier and easier to control to the point where you're able to filter away negative thoughts while indulging, "on a distance" so to speak, with the positive ones. You will be able to enjoy the great and positive events but not relying in them. So you go with the rush when good things happen, and once it's over you're not down but happy for what you had and happy with what you have now. And this is, at least for me, what I want to practice during meditation. The act of meditation being focusing on the breathe and the things around me, to learn how to be in the present moment.

The first time you get this, you get a rush like no other, before it eventually cools down again and you're back to where you were again. But once you've had it once, you know what it is and it'll get much easier to "trigger" in the future. It is not a permanent state of mind but just an excellent tool to use whenever you don't feel in shape due to whatever. With you best of luck :) And PM if you have any questionsat all