That feeling you get...
... when you know you did something right, it's the best thing in the world.
Step back in time 3 years in my career. I was just getting a command of C, had just written a library of functions that encapsulated some pretty hairy business logic into an easy-to-use API. I was new to C, and this libary involved the use of other things that were new to me as well, such as linked lists and tree structures.
Prior to development of this library, it took on average about 3 weeks to develop a new driver for the system. After the library, the average development time dropped to 3 hours. From then on I was basically implementing a new interface for each new system we connected to.
I left that job about 6 months later, but I still do contract work developing these drivers for this company. Yesterday they emailed me around 3:30 with an emergency. One of these drivers I wrote 3 and a half years ago was suddenly giving them problems in a new installation. They were having a demo the next (this) morning, and needed to correct the problem before then. That was going to be difficult because I had to go to Physics class. I got started on the problem at 9:30 last night. It turns out that they are actually connecting to an older vesion of the same system I wrote the driver for 3 and a half years ago. The newer system used to send a command to clear the communication buffer prior to a new command. The older system, from the data capture I received, did not. Solving the problem was as simple as adding a couple of memset() statements to the beginning of the start_new_command() procedure.
I tested the program against the data they sent me. No problems. Turned the program in. No problems. They tested the program against the original system. No problems. They tested the program on the installation site, no problems.
This is the nectar of the gods. Not only was there no problem in the software I wrote, but because of the way it was designed, I was able to quickly isolate the problem and correct it in such a way that it did not impact the original system I wrote against. This is sense of accomplishment I strive for in my work. This is why I love programming.
Happy coding!