Yes, we should express our gratitude to people who help us in times of need. When in difficulty friends, family members are well-wishers would be approached by us. Of the lot, few would promise to help and keep up their promise. We cannot balme people for not helping us but certainly we should be thankful to the kind hearted who have helped us.
At times, there would be good Samaritans who help us with a promise that their contribution should be kept a secret, at such times we have to honor our commitment and keep quiet. But in other situations, we should express our gratefulness to such people and more importantly be there to help them and repay the debt when they are in a difficult spot.
I have known people who are very sweet and humble until a favor is done, once the difficult passes, they also forget the very people who have helped them. This hurts the kind hearted helpful people who would be reluctant to lend future help. Equally embarrassing are the small group of people who help you but never overlook a chance to remind you that they have been of help.
When the favor involves money, we should be very careful about the terms and conditions and honor whatever we have agreed to.