I have two different methods I've used for tracking what I have done. Both work pretty well.
One is the web site IDoneThis (https://idonethis.com/. Its free for individuals. You receive an email reminder daily to log what you did. Either reply to the mail or go to the web site to make entries. You can reply to the mail multiple times to add more entries. It doesn't do categories, but I've hacked the usage to simulate them. Preface each entry with a category keyword, separated from text by ':'. Use the export function to get a list, then put it in Excel and parse data to columns on the ':'. Now I have a category column I can sort and filter by for analysis.
The other approach is Google Calendar. Create a new calendar named Diary. Add it to your default view, set to a different color than your primary calendar. Add entries as desired, including keywords/categories in description or notes. It is very easy to copy scheduled events from your primary calendar to the diary, and then add notes as desired.
Each approach has advantages and disadvantages. IDoneThis is great for a simple list of accomplishments, but doesn't do well at time allocation - I have to enter it manually. Google Calendar is good for getting a quick visual overview of busy/not busy, and tracking actual time spent, but not so good for list of non-scheduled accomplishments. Either one could work for you, depending on what data you're looking for.