People often have a fear that they are going to upset or offend the person who will receive their sympathy words.
Try not to use phrases like "I know what you are going through" - the reason is that you probably don't know what the person is going through, and even if you do it can come across as minimizing the suffering and pain the receiving person is feeling.
Try one of these sympathy messages in your next card:
Please accept these flowers and hear the words we are not able to speak
You are in my thoughts and prayers
With love to you and your family
My thoughts are with you at your time of need
I want you to know that I am here for you at this time of grieving
Thinking of you in these difficult times
Please know our loving thoughts embrace you
Our deepest sympathies during your time of loss. Please know that we are here for you.
Our thoughts and prayers are with you during this difficult time. We are sorry for your loss.
In loving memory of [NAME], [HE/SHE] will be missed dearly.
Please accept our condolences on the loss of your [MOTHER/FATHER/OTHER RELATION].
Our deepest sympathy to you and your family. From all your friends at [BUSINESS NAME]
[NAME] will always be in our hearts and memories. With sympathy, The [YOUR LAST NAME] Family
Keep it short as there is only a small gift card sent with the arrangement.