I think the answer is
I’m aggressive, astute if you will
During a motor race, pitstops are used strategically to try and increase a driver's chance of winning. The timing and number of pitstops taken in a race requires astute decision-making. Refuelling, changing of tyres and other actions are usually performed as quickly as possible so are often aggressive in their undertaking.
My middle and end, will make you go still,
But my end alone, rituals fulfil,
Top - practice makes perfect
My start is deep, but not used anymore,
Pit - pits are often very deep (e.g, a coal mine). I think the type of pit not used anymore might be referring to an enclosure in which animals are made to fight (e.g, a bear pit).
Now find out what I am, that’s what I ask for.