Correct do not cancel your Citi card because if you do you will lower your credit score for two main reasons. First you will potentially hurt the length of your credit history – the longer you have a credit history the better it is, especially if that was the first credit card account you opened.
But since you have so few cards, closing that account will hurt your debt/credit ratio because you will no longer have that amount as available credit:
for example
say both cards have $5,000 credit limit, giving you a $10,000 total, closing one will give you available credit limit $5,000.
But if you charge say $1,000 and pay off each month totally, you still have used 20% of available credit at the time vs 10%.
If for some unfortunate reason you need the credit card for expenses because of a jobless or illness you can use it, if it is closed you do not have that option anymore – especially losing a job since you can not apply for a new card without a job.