Well i have herd it before and i have herd it again. "My spells don't work i am giving up" well this makes me laugh, so i thought i may shed a little light. Your spells don't work because:
Inexperience: This is usually the case, and because of this we lose out on people who have potential, but give up after a failed spell, because they haven't stored enough energy mass. Do you basics newbies :)
Psychically impossible: Mermaid and vampires (my thought on vampires are all over the place at the moment but a spell would not make you one) will not nor ever work, first off, science has proved that there is energy's at work all the time, just not what they are and what they can do, and that's all a spell is, energy
Not believing in it: You need to believe people, the power of positive thinking :P
The will of the universe: Some times the universe will decide you don't need money/love or anything you can come up with at the moment, so sometime's it is just the fact the universe knows you don't need it at the moment.