Every 10 mmHg reduction in systolic blood pressure lowers the risk of heart attack, stroke, and heart failure by approximately one fifth. This effect has been demonstrated in large, well-designed studies that establish cause and effect, including in mildly elevated blood pressure. Lifestyle measures and medications are both effective means of achieving this.
Every 10 mmHg drop in your systolic blood pressure reduces your chance of a heart attack, stroke or heart failure by roughly one fifth. That is no small gain, and it applies even when your blood pressure is only mildly elevated, not just in people with a clearly serious problem. The studies here are large and well designed, and they demonstrate cause and effect, not merely an association.
The four levers that genuinely work are: eating less salt, losing weight where relevant, exercising more, and drinking less alcohol. Each of those four lowers blood pressure independently, and together they add up considerably. If lifestyle changes are not enough, or if blood pressure is high enough to warrant it, there are medications that are safe and effective, but the decision about how far to lower it and with what depends on your age and overall health, and that is something you work out together with a doctor.
To know where you stand, measuring at home is more reliable than a single reading at the doctor's office, because white-coat effects and incidental spikes can distort the picture. A validated upper-arm monitor is widely available; measure a few times a day at quiet moments and write down the values. That way you see a real pattern rather than a snapshot. That pattern is the most meaningful thing to discuss when you then look with a doctor at whether action is needed.
Overview covering multiple factors (2 research records, 3 sources). The strength of evidence differs by component -- read the answer for the nuance.