hi Entheologist,
i believe some are thought forms, fragments of energy we create, and some are thought forms, entities, or fragments of energy that are already created and we attract to us (form situations or people).
So if we are "magnets" for these kind of energies the thought forms are just around us, passing through us and attached to us.
The key in removing these perpetual negative energies existing everywhere is to "bring light to the drakness" I.e. making the fears, programs, and thought loops that attract and feed these energies conscious and known to you in a conscious way.
The second important element which is the same as the first concerns to "cleaning and cleansing" ourselves by means of acquiring knowledge and self knowledge. Negative energies will always be around but it is us who resonate with them, the more we work on ourselves in a STO way the less we resonate with these energies.
For example the fear of the dark, or spiders, this fear creates any number of though loops, and emotional distress that ultimately attack energies or entities hungry of these emotions. By making the self aware and conscious of the nature of the fear we are less likely to fall into dissociation, thought loops and distress and can ultimately find a resolution and peace with the fear.
There is one thing i would suggest you contemplate, since you ask about the creation and dissolution of thought forms, and starting to answer these question may give you a better knowledge and understanding of the nature and origin of our Human thoughts,
we need to learn how to think. How do you think? what is the process involved in thinking?