How can you avoid to lose a train of thought during your presentation? There are various things you can do. Obviously you need to prepare and practice to memorize the topics you want to mention. Putting (a summary) of the topics on a presentation slide may help you not to forget any of the items. Having a screen with the speaker notes on a screen in front of you (not visible to the audience) may also be supportive to ensure you don’t forget anything important.
If you are using a list of items as support, then don’t get too occupied with looking at this list. You are presenting to the audience and not to a list as shown on a screen or on a piece of paper. After you have presented the list of the things that you remembered it is also ok to tell your audience that you will quickly check a list on a piece of paper to unsure that you covered all items on the list. It is ok to be open about it. For more tips about how to avoid losing a train of thought during your presentation, you may want to have a look at the various tips and tricks in the book that is part of the Public Speaking Kit.