[smokel]

I find that exercises without answer help me to build confidence. It requires me to be sure of every step, and the actual answer is less relevant.

Of course this all depends on the type of exercise. For some, you can easily check the answer yourself after you have found a solution.

Also, in the real world, most assignments don't have an answer either, and it seems like a good idea to be prepared for that.

[dunefox]

In the "real world" all assignments I had had answers. To quote a mathematics professor, "how else could I expect you to understand the material on your own, outside of my lecture".