In my experience it honestly depends on what kinds of spells you are doing. Because some like curses or revenge spells having strong emotions will make the spell stronger. However, emotional pain during spells may make them back fire or draw negative entities to you to feed off your pain, or they won't work how they are intended.
I was warned to never practice healing on another person when angry or upset because my own negative energies could be transferred in such cases.
In some cases emotional problems can manifest as energy blockages, which affect the general channeling of energy. Deep-seated anger, pain and resentment can lead to the accumulation of diseased energy in the body, the chakras and the tissues of the body. It can manifest as physical ailments over time.
Sometimes treating the energy body alleviates the emotions. Though it doesn't necessarily get to the root of the problem. The lower emotions like anger and jealousy accumulate in the solar plexus. Intense grief can accumulate in the heart. Problems with expression and repression can manifest in the throat, ajna and sex chakras simultaneously. Strong suicidal feelings also tend to indicate a depleted base chakra, among many other problems. Cleansing and energizing of the chakras can make someone feel much better, up to a point.
The other aspect to look at is the thought entities created both by the person and those that are attracted to him/her and are feeding of the emotions or habits. These too can be brought to light and destroyed/disintegrated. Most people have their demons, and curing the psyche is like peeling away layers of an onion. You tackle one area of problems, only to find several underlying issues beneath. It takes patience and honest self-searching to know oneself, and much more for another person.
I personally do not believe in using curses. What you send out returns to you many times over. It may be our Karma to work through certain problems at certain times in our lives. Refusing to learn these lessons would make the future lessons harder. It is better to "work out our salvation in fear and trembling".
If you are not in the right emotional state, you can try to "transmute" your emotions. Is a bit tricky, but it works.
Consists of transform negative emotions into positive, not eliminate the negative, transform them, take advantage of them. As the negative emotion is detected, it is consciously directed towards the desired positive emotion, fear becomes confidence, anger becomes happiness .... Very useful when working with spirits.
Speaking of transmutation, Noscete, I was taught to use the Prayer of Saint Fancis of Assisi as an active meditation.
When you meditate, actively go through the negative emotions and transmute them into positive ones. It takes a lot of practice, but even when done imperfectly it has a strong effect.
Lord, make me an instrument of Your peace.
Where there is hatred, let me sow love;
where there is injury, pardon;
where there is doubt, faith;
where there is despair, hope;
where there is darkness, light;
Where there is sadness, joy.
O divine Master, grant that I may not so much seek
To be consoled as to console,
To be understood as to understand,
To be loved as to love;
For it is in giving that we receive;
It is in pardoning that we are pardoned;
It is in dying to self that we are born to eternal life.
Never heard that prayer, I was educated in Catholicism but never got to believe.
It is true that the technique is powerful, stronger the negative, stronger the positive once transmuted. It has allowed me to work better with some tough spirits.
There is no straight foward answers as many factors play a role in how a spell is effected by your intent,emotions,ect. And what kind of spell would you be casting? This question that you asked can only be answered with vague answers. If you provided more information to what you mean, perhaps a clearer answer I could give.
