And sadly enough, you aren't trying your best. Patience is what most people lack, which is why many fail in casting spells.
Remember, it is not that you had powers and now it is lost. Everyone can do magick.
Magick is not only about casting spells. Start over with the Basics slowly and patiently, practise them thoroughly. With due time and patience, I am sure you will get it right.Then and only then, you may move on to spells. There is no easy and fast way to magick, it needs patience and time.