Improve your fluency when speaking
Mistakes are simple slips of the tongue or minor inaccuracies in your English that don’t affect the meaning of what you are saying. They are a common feature of normal speech and do not need to be corrected, especially as people are much more interested in what you have to say, rather than how you say it, and mistakes often go unnoticed. Correcting a mistake simply draws attention to a problem that may in fact not exist in the first place; and in so doing, it disrupts your flow and detracts from your message. In this situation, fluency is much more important than accuracy.
Errors, however, are those problems in your English that do have an effect on comprehension, and it is therefore vitally important to correct errors immediately, otherwise whoever is listening to you will have difficulty keeping track of what you are trying to say; or worse, they may not understand you at all. In this case, fluency must be sacrificed in favor of accuracy.