Writing clear, direct English is particularly important in a business context.
Please rewrite the following item (there are many different but correct ways of doing this):
I really can't thank you sufficiently for lovely gift I was given on the occasion of my retirement from the company. It is something that will always be appreciated by me, and it will also serve as a reminder of the many happy that have been spent working for the company.
Hint: Check Chapter 9 of Barron's Business English, and avoid using the passive voice and other wordy constructions!