Problem solving. The sense of accomplishment when solving a really complicated problem cannot be beaten. There are always new problems to solve, solutions to find and bugs to fix. The non-repeating nature of the subject implies that each new challenge you solve will teach you something new in return and make you a better programmer.

Constant learning. Programming languages are constantly progressing and getting better, therefore you will find yourself learning all the times. Programming ecosystem is rapidly changing at a fast with new frameworks and tools appearing sometimes way too often. It is not happening to deliberately mess up your life. It happens because programming advances and that is a thing to get excited about!

Challenge. Many aspects of programming are challenging. Building up requirements, designing clear and scalable systems, writing efficient code and debugging in a multi-threaded environment are not easy tasks. Surprisingly, mental challenges are one of the things that excites the most. Programming languages have strict logic that you must comply with at all times, but there is almost an infinite number of ways to write a program to solve given problem.

Creating something that didn't exist before. Programming is creation in a sense that something new comes existence. Client gives you a task or a problem to solve and at the end of a day you have a ar new product that wouldn't exist otherwise.