Services (Mssql, Sql Server Agent)

First I created an NT account " xyz " and gave it an admin right. then,
I opened Control panel/service tab, selected Mssqlserver and clicked on startup botton. I choose log On as This account and I selected xyz account from Win NT . Once I selected the account I run "start the service."

I did the same thing with the SqlServerAgent, and MSDTC.

Here is my question.

What if I am the Admin person and I use my logname and password in these services. What is the impact in doing so. Or it is better to designate one account (xyz) for these services and not use the account else where.

Another Question is that when I start the service and open the enterprise manager, Do I need to add xzy account in the security tab of enterprise manager and assign server roles to xyz account. What do I gain in doing so and what do I not gain if NOT doing so.


I do not know the answer, If you do have insight in this please let me know

thanks

Ahamed