I completely agree with what Sue said here ^^
I would also like to add that it depends on what spell you have cast. It's obvious that not every spell will work, some of the spells are real magic spells and some of them are fantasy / fluffy spells. So what you also need to know is which spells are real magic spells, and which spells are not.
Firstly, to make sure that the spell has at least some potential to work, you have to make sure that the spell is a real magick spell that is actually connected to magick and its practices.
Just remember that there are two types of spells:
Real magic spells - These are real magic spells that actually work for the magic practitioner if he/she casts it properly. Such spells will work for you if you know what you are doing, if you are experienced and familiar with the basics, and work better if you will choose to follow some optional traditions like : colors, planetary days and hours, moon phases, ritual tools and supplies, etc. Such spells always worked for me if they were casted properly, since they are magic spells that have potentiaby l to work,. Do not forget that this is about potnetial, and such spells really have it. By saying real magic spells i mean that these are magic spells that can be cated by magic practitioners. Such spells do not include physical changes and DNA changes, or any actual kind of transformation. This is the other sort of spells i am going to talk about.
Fluffy / fantasy spells - Such spells are not real magic spells. The magic practitioner will not be able to get results from them even if he dedicates as much energy as he can, and even if he / she follows all of the traditions and optional things. It means that they have no potential to work. No matter what the magic practitioner tries to do, and how. Such spells include : transofrmation, DNA changes, and other kind of things which can be found only in science fiction movies. You are able to avoid such spells by : personal experience, logic sense and maturity.
This thing is very important. The proper spell has a lot to do with managing to cast the spell, it gives the spell most of its potential to work, as i said.
Also remember to go to the 'tips' section we have here, which gives optional and good tips for casting :