Another problem is that some people have poor visualization abilities. If you don't visualize well, try another modality, i.e. have your fantasies more in words and feelings. Through practice you can develop a more vivid fantasy. Effectiveness, advantages and dangers Fantasies do generate feelings. There are few experiments in this area but many clinical reports of distress brought on by unpleasant memories and thoughts about possible disasters.
Some actors create tears by thinking of a sad event.
It is reasonable that positive emotions can be created in the same way. The advantage is that these methods are simple, straightforward, and done on your own. There are no known dangers.