Help please?

Hey Guys,
Can someone tell me why, whatever I do I end up losing?, I can win some hands but it doesn't last, I will end up losing in the long run so when I can see that's going to happen I quit and save my money because I don't know what else to do.
Picture the situation, I'm sitting at the table and the cards come, I have to make a decision do I hold or do I fold?, there's far too much info and opinions about this question without getting to the ones about calling or raising.
Can someone please recommend some literature that's worth reading (i've read plenty that doesn't work in practice)
I would like to improve my game and make some money at this or get thro' to final table in tournaments even if it's only in a small way.
I have made final table before in two small paying tournaments but it was just luck rather than knowing what I'm doing and when to do it with every hand.
I can't do grinding as I don't have the money or time even when I've learn't what to do, I can only play one table so any advice would be much appreciated.