Sometimes you'll do a spell and it won't work. This isn't necessarily a sign that you didn't do it properly, they just sometimes don't work. Usually with Hindsight we realise why the spell didn't work. Usually this is because with hindsight we realise that what we wanted then wasn't the best thing for us, and that we wouldn't have been happy had we got it.
There are several reasons for spells not working, and I'll try and show you some of these.
There is a saying that goes "Be careful what you wish for, you might just get it!" To most people, that is an encouragement, but to a Pagan, we realise that it is actually a warning. Be careful how you word your spells, and be careful what you ask for, because sometimes what we ask for, and what we really want are two separate things. For example, if you need money for something, and you do a spell to "bring me money". That sounds like a reasonable request, doesn't it? How much money do you want? where do you want it to come from? You may find a dollar in the street, money came to you, perhaps not what you had in mind but you got what you asked for! If you win the lotto, and receive money, that is great - and usually what people mean, however if your aunt died and left money to you in her will, you would still be receiving money, but to the sacrifice of something else. Be careful how you word your requests.
Another problem is when you ask for "love", "Happiness", "Lots of money", "wealth" or something like that. These have not been given a value. How much money do you want? What do you define as "lots"? What type of love do you want? Brotherly Love? love of a partner? .. a pet to love? What do You define as happy, what makes some people happy doesn't make others happy. I believe that the Goddess and God know what it is we want, but I think they chose not to grant it if we don't ask properly, just to teach you to ask properly next time! A lesson not to be lazy next time and ask for what you want.
So when you are asking for something, make sure you are as specific as you can be, even if that means writing down every aspect of the wish. That way, the Goddess and God (and yourself) know exactly what you desire, and you stand a better chance of getting it
Some spells have to "Grow" and therefore need time. (Rome wasn't built in a day.) Some spells may work quickly, others will take time to achieve. Don't be impatient. If you don't feel that any progress is happening, then retry the spell. If you still don't think anything is happening, then maybe look at the spell and work out if you are aiming for the right thing, and if the spell is worded correctly.
Intent - Putting the energy into it
A spell is basically a way to focus your intention, and to give it power to help it manifest in the physical world. When you do a spell you have to want the outcome with every fibre of your being and you have to focus on what you wish to achieve and send energy towards that goal to make it happen. While some spells might work if you don't put the energy and intent into them, if you want it to happen, put the energy into it. While doing the spell, visualise what you want to achieve see yourself in the job, or see yourself getting a brand new car.
Spells for the wrong thing
Sometimes healing spells will not work because as much as you are wishing the person to get better, they themselves are wishing to remain ill. It sounds very strange, but some people actually like being sick (they get attention, want to punish themselves or for other reasons), or they may subconsciously holding onto something that is making them ill. In these cases it is best to do a spell to help them heal any inner problems they may have before you try to heal the physical problem, which may just be a symptom of inner/emotional sickness.
Try to look for the problem, and do the spell for that sometimes the problem manifests a symptom, and if we do a spell for the symptom, it won't help (or maybe won't even work) because the problem is still there.
Not the right thing for you (at that point in time)
If you don't get your wish, even after asking properly, putting the energy in, doing the right kind of spell and waiting a while, maybe you aren't destined to have whatever it was you asked for. Although it might not make sense now, you'll most likely see later on that it wasn't right for you. Or not right at that time.