Tachycardia. Medicine needed lifetime?

I am suffering from tachycardia issue since few years where my heart heart during active hours is always above 120 and goes above 160 with activity like walking and even slight activity takes it over 100 but it is normal when resting usually 60-75 so i consultanted a cardiologist here who performed echo and ecg and all came normal and he prescribed enapure 15 mg once daily but  my physician changed that medicine to Metocard xl 25 and taking it since few years and heart rate was under control  but I recently tried to stop my meds although i had no symptoms but my smartwatch constantly show high heart rate above 120 when active but normal resting rate what can be done in this case medicine needed lifetime? and which medicine is best i don't have any other problem like bp or diabetes although a little high triglycerides nothing else.