It can be silly but still true that sometimes I feel a bit overwhelmed. I have had much more demanding schedules than I do now and had no trouble with them. Pesky feelings of too much all at once tend to pop up in the morning. While I wake up, I start to think of what is on the calendar for the day. Several items push their way into my mind, even though there is no rush.
I have found the best thing for me to do is to make a list. Not fancy, just paper and pencil. I have often found that it is making the list that is the most important thing. I don't like to lose it but once I have made a list of things to do that day, I can usually reconstruct it from my head if needed. Reconstructing it goes better and more smoothly if I again sit with pencil and paper and write down the items.
The items that I want to get done (truth is that few if any really NEED to be done) often crowd like an unruly gang, all seeking immediate satisfaction. Each item presents itself as needing all the other items done simultaneously or better yet, beforehand. Telling myself that my mind is being silly doesn't do much to quiet the noise. Making a list, which seems to mathematically require an order, is acceptable to my inner child, helps and gives me a sense that the day is laid out in a way that will lead to completion.
I often made a list of items to be dealt with in a class or presentation or lecture. I had trouble making myself consult the list during the class and if I did forget or skip an item, I wouldn't know I had done so until the class was over. Then, I would pick up the list and look at each item, spotting an omitted item or two. A little mental cussing would occur and I would pocket the list for use in making the next one.