Habits and emotional responses that you've learned in over a dozen years of test-taking aren't going to suddenly vanish, but keep in mind that your ALEKS assessment is very different from most other tests. Here are few pointers for getting an accurate ALEKS assessment.
Take your time
You have 48 hours to complete each placement assessment. If you don't complete your assessment within 48 hours, no big deal - just start a new one later. Incomplete assessments don't count towards your total of five placement assessments.
Take a break
If you feel impatient or stressed, take a break and come back when you're ready to slog through some more problems. Get up, walk around, swear and make obscene gestures at your computer, get some sleep, listen to some upbeat music, have a snack, ... do whatever helps you to settle your nerves and regain your concentration. Most students spend roughly a total of two hours actively working on their assessment, and you have 48 hours from the time you start to the time ALEKS will declare "time's up", so don't power through in a single sitting unless you're comfortable doing that.
Don’t answer “I don’t know” unless you really don't know what to do
Don’t skip the word problems
DIY
While you're taking your assessment, resist the temptation to Google that trig identity or ask your roommate to remind you how side-angle-side works. You'll have ample opportunity between assessments to brush up on material that you almost, but not quite, remember. ALEKS will assign you a Learning Module based on your initial assessment, and it's in your interest to get the Module that's the best fit to your actual current skills. Hopefully by the time you reassess, you'll have enough confidence in ALEKS and yourself to tackle the assessment on your own, knowing that you can continue to fill in any remaining weak spots.