You've likely seen fish oil for sale at the grocery store, and if you're not supplementing your diet with Omega-3 fatty acids, I'm hoping to convince you that it's worth your trouble and money. The name "Omega-3" is derived from the chemical composition of the fatty acid; the first double bond is 3 Carbon atoms away from the methyl end (the Omega) of the molecule. Here's a diagram of Eicosapentaenoic acid (EPA):
(By Edgar181 - Own work, Public Domain, https://commons.wikimedia.org/w/index.php?curid=2962205)
EPA, DHA (Docosahexaenoic acid) and ALA (Alpha-linolenic acid) are the three most important Omega-3s in our bodies. Plant sources are full of ALA, while animal sources are full of EPA and DHA. We can convert ALA into EPA and DHA, but not very efficiently, so it's best to get EPA and DHA directly from animal sources. Omega-3 fatty acids play a role in cardiovascular function, our nervous system, and our immune system, while also being anti-inflammatory. In addition, they are a key component in our cell membranes, which are fat-based. Omega-3s keep our cell membranes permeable and allow the easy transport of neurochemicals (such as serotonin) into and out of the cell. At the same time, a proper level of Omega-3 fatty acids increases insulin sensitivity, resulting in the uptake of insulin and consequently the uptake of blood sugar for cellular energy. Getting the right amount of Omega-3 fatty acids will allow your body to function calmly and efficiently, and several studies have returned promising results from introducing Omega-3 fatty acids into diets; this study showed positive behavior change in a group of children living in Maritius, and this study showed remarkable changes in the behavior of incarcerated adults.
Omega-6 fatty acids are similar to Omega-3s, but their first double bond is at the 6th Carbon atom from the Methyl end of the molecule, and Omega-6 fatty acids are inflammatory. We need both 3 and 6, but today's modern diet is heavily skewed towards Omega-6 fatty acids. It's very likely that your ratio of Omega-6 to Omega-3 fatty acids is too high. In order to correct this, you should avoid refined and processed foods, eat a variety of plant and animal foods, (in particular fatty fish and wild game), and consider taking a supplement such as fish, krill, or algae oil. Wild fish will be higher in Omega-3s than farmed fish, and krill oil is the most eco-friendly and potent source of Omega-3s.
I hope this information is useful to you. I am continually amazed by the profound yet simple solutions nutritional science is uncovering. With knowledge such as this, I believe we can change ourselves, our institutions, and our societies for the better.
Other sources: Essentials of Sport and Exercise Nutrition, 2nd Edition