Schema design for journal website speed

Hi, I was hoping for some input with a schema I am creating. I have made a journal website where currently 1000 active users each day write a journal entry, rate/create goals (which can change) and record there dreams. I made the db fast and just embedded everything in each users documents. Now however, the documents are getting pretty large and need a better schema that will scale with many more users if it becomes a popular website.
It is important I can get a whole months’ worth of records for a user when they log on as my front end displays many graphs to display their progress.
People have suggested I create a new collection (still keeping user details collection) where each document stores a users recorded journal data for that day. Then I use a compound index with user id and date to find those 30 days when they log in.
I am completely new to mongodb (confidant in sql)
I am worried however when there are 1000s + insertions and reads a day of the performance.
I was wondering if anyone knew any good ways to store and access this kind of data.
Also, would It be faster if instead of storing individual days, I instead stored a whole month of data in each document ?
Lastly, If I do store whole months, Should I link the months to the individual like this:

{
    "_id": "23h4k2j3khkj3h"
    "name": "john",
    "password": "apple",
    "months": ["ObjectID('AAAA')", "ObjectID('BBBB')", "ObjectID('CCCC')"]
}

Or simply store the user id in each month.

Any advice would be great and happy to clarify any confusing points.

Thanks and have a great day.