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I think I'll give my opinion on this matter, precisely because I have found myself having the same experience – and to a certain extent, overcoming it. A small amount of background: I am by no means an experienced mathematician, I am entering a master's program in the fall and intend to continue with a Ph.D. program afterwards. As such, I am taking the Mathematic GRE subject test in the fall with the intention of boosting my score to the $n^{th}$ percentile for $\lvert 99-n\rvert<\epsilon$ for all $\epsilon>0$. Whether this comes to fruition or not, the review process is annoying. I think I have found some effective techniques for reviewing otherwise dull material – Calculus, Elementary Linear Algebra, Basic Algebra, etc. Here are some thoughts.

(1) First and foremost, when reviewing a more basic theory, I try to see how it ties in to more advanced subjects I have been learning about. For instance, much of the theory of Calculus of Several Real Variables lends itself to generalization to $C^\infty-$ manifolds and Riemannian Manifolds. I have been trying to make sure all of these more basic results are integrated into my understanding of Manifold theory. I have found quite a few gaps in my understanding of the latter in so doing.

(2) If you're reading something that you really do know quite well, see if you can recreate it from first principles, and see how slick you can make your proofs. Not only will this help you organize and remember the information, it will help you as an expositor in the future if you record these notes. Alternately, you can create some sort of lecture series on a blog someplace, as mentioned by another user in the answers.

(3) If you are in a university setting, sometimes tutoring material you want to review is quite beneficial for both parties. If you aren't that comfortable with the material, then maybe don't charge money, but find a friend who is struggling, and explain the material to them. If they are particularly inquisitive, you may finding them asking you things that you can't immediately answer.

(4) You can always just jump to the more advanced subjects that do interest you, and refer back to the basics as necessary. Sometimes, seeing the utility of the elementary material can help motivate you to study it. Indeed, for me, a lot of basic manifold theory used tricks from multivariable calculus that I was not as familiar with as I should have been. This certainly made me review the basics.

(5) The last piece idea I will propose is to seek out hard problems. And I do mean rather difficult problems. Sometimes, racking your brain for ideas when you are stuck forces you to review the material at hand without even realizing it. Moreover, these sorts of problems will improve your general problem solving skills, whilst allowing you to review basic materials, thereby killing two birds with one stone.

I hope this helps somewhat.