Yes! You are able to go back using your online or app account to re-play any session you wish.
To do this, just scroll back to previous 'packs' (E.g. The Discovery Series, Heart Series) and click on the 'day' number you wish to re-play.
This will allow you to develop your practice and re-go over sessions if you find it useful. You may also like to go back and re-do a shorter session if that is more convenient for you on any particular day.
Current technical functionality means that after re-playing an already 'done' session, your online or app account will automatically take you back to your 'current' day. You'll therefore just need to do the above each time you wish to re-play a session.
We hope this helps, and happy meditating!