Meditation is a reading and understanding of the Book of Life. We have many daily problems (activities) in this world. Meditation allows all this activity to settle down and often results in the mind becoming more peaceful calm and focused. In essence meditation allows the awareness to become 'rejuvenated'.
Experiences during meditation probably vary significantly from one individual to another or at least if different techniques are involved. Relaxation increased awareness mental focus and clarity and a sense of peace are the most common by-products of meditation. While much has been written about the benefits of meditation the best attitude is not to have any expectations when practicing. Having a sense of expectation of (positive) results is likely to create unnecessary strain in the practice.
The most people can successfully practice aerobics or body building for instance without knowing human anatomy or without understanding at all what they are doing or why. Without knowing exactly the nature of this process it is impossible to correctly realize it and therefore there can be no true meditation. Meditation is the highest degree of concentration. In fact very few people can really meditate and this for two main reasons:
Very few know exactly what meditation is;
Even fewer are willing to comply with it (lack of motivation).
Keep in mind that meditation especially in the first stages must have an object. Without object to meditate upon there is no meditation. The simplest object of meditation is a physical object (any object which created by God a flower a tree a scenery etc.). In more advanced stages the objects of meditation become ever more subtle: mental images created at will a piece of information a problem that needs a solution a feeling a thought an idea a subtle energy a state of consciousness etc. In this material the word "object" will refer to any of these.
As well since meditation involves becoming more aware and more sensitive to what is within you facing unpleasant parts of oneself may well be part of meditation. Regardless of the experience the meditator should try to be aware of the experience and of any attachment to it.
Failure to experience silence peace of mind mental clarity bliss or other promoted benefit of meditation is not in itself a sign of incorrect practice or that one can't concentrate properly or concentrate enough to be good at meditation. Whether one experiences peace or bliss is not what is important. What is generally considered important in meditation is that one is regular with their meditation -every day- and that one make a reasonable effort but not strain to remain with the object of concentration during the practice. With regular practice one inevitably acquires an increased understanding of and proficiency with the particular meditation technique.