If your heart isn't in it, please don't do it. That being said it will be the best way for you to hone your flying skills and knowledge of the rules if you do it properly.
Was once explained that an instructor will pass 60% of what they know onto the student. If you (having been that student) don't apply yourself to bring your 60% back up to 100%, then you can see that 60% of the original 60% means not much is being passed onto the second generation of students.
Totally agree with Lexair in that instructors are undervalued in the industry.