Try throwing a pebble into a quiet lake. Centered from where the fall of the pebbles will create a ripple of waves that flow into the lake.
Now, can you stop the wave ripple? Maybe you try by putting your palms into the water. Or. block it with both legs. But what happens is that the more you do something on the surface of the lake, the more new wave ripples emerge. The only way to stop the wave ripple is to let it stop by itself.
So it is with calm and mind. The harder you do something on your mind. the harder you get that calm. Just watch it.
Do not reject or stop the ripple of your mind. Let the mind gradually calm down. Calmness begins with peace of mind; while the peace of mind starts from the calm of breath. In a quiet breath find a quiet soul.