1. Flat boring and unflattering hair.
When your hair no longer frames your features and the top is flat and it seems that it just sits there on top of your head lifeless even after you blown it dry, set or even curled it. Do get a trim to give it volume, character and would frame your face better!
2. Dry, Damaged, Unmanageable hair.
Years of aggression from different styling tools, lifestyle, unhealthy habits, stress and weather conditions can alter your hair, especially the end part of your hair. Chopping it off would be a great option. Especially if you have split ends. It goes up even more, but for the mean time, if moisturizing your hair still helps, try cream based styling products or serums. It would leave it supple and less tendency to break.
3. It takes a lot of time to style your hair.
maybe you're too particular in making it too perfect, or you want to alter your hair texture into the polar opposite of what it should do, or the cut is not making the most of your hair texture.
4. Your crowning glory doesn't recieve compliments as they used to or at all.
You deserve it. Having a great-hair-day is not enough. it should last more than that. Make the most out of the style and change it up a bit. Set it in hot rollers, to create the soft waves, use curling irons, flat irons and the likes to moderation.
5. What you wear or who you are now doesn't reflect what your hair should be like(vice versa).
As you evolve, your hair should too! It should reflect how you feel about yourself, and who you are as a person, wether your determinant may be your job, your weight loss, lifestyle.
6.You sport your hair in one particular style all the time.
If your work requires you to pull it into a pony or bun most of the time or your lifestyle, consider bangs and layers to make it interesting and with a shape so you may be able to opt to wear it down since it's stylish to be worn in one style most of the time. If bangs are really not an option for your lifestyle, then maybe trying on a clip on bangs. :) And also make sure that you would at least dry your hair properly before tying them. Your hair are at it's weakest point when it's wet.
7. Colleagues from your past comments on your look that "you haven't changed at all"
Run the opposite direction and opt for a change! It's about time. Get inspirations from celebs to normal people who share the same face shape, "taste", and style you might consider. If you can picture yourself looking like them and having it, next step would be scheduling an appointment with your reference. :)
8. Your stylist gives you the same hairstyle.
It's either you give your stylist your pegs s/he will work on, or meet halfway with the style you're aiming for if it's doesn't necessarily suit you and work it to your advantage or just shift to a new pair of vision with a new stylist.
9. Your skin and hair are like your foundation in perfect match!
So far, in the fashion industry, this is a NO-no! it doesn't frame the face one bit and would add weight and zero dimension. If this is the case, consider having low lights. (it's the reverse of highlights, it's darker than your base color and highlights.)