I have known about trimming natural hair for sometime now but I did not see the reason why I should take off some inches from my hair to make it healthy. But after going through a phase where my hair tangled up and broke a lot, I finally saw the reason why I should and the difference was quite clear.
Hair trimming is basically getting rid of your damaged ends which could be caused by over manipulation or use of heat. To trim your hair is to cut off the split ends in your hair.
Trimming your hair doesn't make your hair grow faster. It doesn't affect your hair growth rather it helps keep your hair healthy as it grows. There is this misconception that trimming your hair regularly will make your hair grow faster, well that's not true.
Looking at it plainly you are taking off some inches from your hair instead of adding to it, so why then do you need to trim your hair?

WHY YOU NEED A TRIM
Although many of us want to preserve our length, hair trims are necessary. In fact, we need trims to keep our strands healthy and strong.
The ends of the hair shaft can begin to split for different reasons ranging from previous hair damage to over manipulation.
Going too long without a trim can cause further splitting of the hair shaft, this can result in breakage, and often times visibly dry, brittle ends.
Hair that needs a trim can also be one of the reasons why your hair does not appear to be growing. Leaving your hair untrimmed will cause your hair to break more often thereby making you lose your new growth.
3 SIGNS THAT YOU NEED A TRIM
1) INCREASE IN TANGLES/SINGLE STRAND KNOTS
If your detangling process becomes increasingly more difficult and time-consuming, this can be one of the signs its time to trim your natural hair.
More specifically, if you are getting multiple single-strand knots throughout your hair, it is time for a trim.
Single strand knots are normal with the different type 4 hair ranging from a to c. The density of afro-textured hair tends to cause them to intertwine with each other.
While it is expected to have single-strands knots, over manipulation can cause them to worsen. One way you can limit tangles is by keeping the hair strands smooth by moisturizing it. Keeping your hair stretched by braiding or twisting them can also lessen the tangles.
2) WHEN YOUR ENDS FEEL ROUGH
Another one of the obvious signs that it's time for a trim, is if your strands feel rough and brittle. While our natural hair is naturally prone to dryness, excessively dry hair can lead to rough and brittle ends. Then the natural oils our hair produces at the root will have a difficult time traveling down to the ends of our curly, coily, and kinky strands.
A good trim can help to make your hair appear and feel healthier. However, consistent moisture will alleviate dry ends.
Try to keep your hair moisturised and your ends sealed as much as possible to keep your ends healthy and lessen the number of times you need a trim.
3) SEE-THROUGH ENDS

Hair that is see-through at the ends may have some sort of underlying damage caused by heat damage, chemicals, etc. Using heat tools or chemicals repeatedly causes the ends of your hair to become thinner than the rest of your hair. If this is case, then you will have to trim the ends of your hair to restore your hair back to health.
BENEFITS OF TRIMMING YOUR NATURAL HAIR
1. HEALTHY HAIR GROWTH
Trimming your hair may seem like the very opposite of retaining length but I can assure you that it is not.
The benefits of trimming hair are immense.
When you trim your hair you are taking away the parts of your hair that are doing more damage than good. This gives way to the ability for healthy hair to begin to grow.
2. IT HELPS WITH HEAT DAMAGE
The main causes of heat damage are usually hair straighteners or blow-drying.
Unfortunately, once you have heat damage you can’t repair it. Once your hair is heat damaged that’s pretty much it. The two options you have is to either cut it off and grow it again or trim it every month till the damage is gone.
3. EASY STYLING
Having ends that are damaged just don’t look great on some styles like twist out, braid out strand twist etc. It makes styling much more difficult because it is almost like working with two different textures of hair.
Damaged hair tends not to do what you want it to which makes styling a bit harder.
4. MAKES HAIR LOOK THICKER
Once you start to trim your hair your hair will look much thicker and healthier from the root to the tip.
5. PREVENTS SINGLE STRAND KNOTS
There is not really a whole lot that you can do to prevent single strand knots but trimming your hair will reduce the rate at which they form.
Also keeping your hair in a stretched out state can help to reduce the effects but you might not always want your hair stretched.
6. EASY DETANGLING
Trimming your hair regularly can cut down on the time it takes to detangle.
The process of detangling is made much more difficult when you are faced with having ends that are not in good shape you will likely have to manage split ends, single strand knots and breakage.
Two ways you can trim your natural hair.
1. When wet
You can choose to trim your hair after your wash day when your hair is still wet and moisturized.
2. When dry and stretched
You can also trim your hair when it's in a stretched state. This makes it easier for you to see your split ends.
It's best to trim your hair using a sharp professional scissors. Using a blunt scissors will cause more split ends.
HOW OFTEN SHOULD YOU TRIM YOUR HAIR?

It's best to trim your hair every 4-6 months. To avoid trimming your hair as often as every 4-6 months, then you'll have to manipulate your hair less and trim every 6-8 months instead, in my opinion.
If you manipulate your hair a lot, probably because of your lifestyle then you would have to trim your ends more often than someone who doesn't.
If you think you'll cause more damage to your hair by trimming it yourself then it's best you go to a professional stylist.