Use sincere and meaningful adjectives. (Sincerity is very important.) Perhaps:
.
Thank you for the wonderful card and the beautiful vase with the lovely flowers inside. It makes me feel very good to have received such lovely gifts. Every time I look at them I think of your kindness. I think of the wonderful people who sent them. I am very grateful for your wonderful gifts. You have contributed to many pleasant thoughts. Thank you. Thank you. Thank you.
Sincerely,
Bob Hope
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