Is There a Structure to Taking out Invisalign Aligners?

There are little plastic tools with hooks that can be used to remove aligners. These are particularly useful for those with short fingernails.
Often, removal of the trays becomes more difficult during the first few days when the aligners are tight, if there are severe undercut areas, or multiple attachments placed in one arch.
With attachments, it is usually easier to remove the aligner starting from the palatal or lingual side at the back. This way, you are pulling the aligner out and around the attachments, making it also less likely to debond your attachments.

Often it is easier to ease one side off then the other, depending on if the teeth are crowded more on one side than the other. Also, if you have attachments on the some of the teeth, these areas will be more retentive and harder to remove. It is not unusual that especially at the start of treatment, it's a little more challenging to remove the aligners. It's a combination of the tightness of the trays and also the dexterity that removing and replacing the aligners requires. Keep up with it! It should get easier every time.