You need to make sure you're within the centre of gravity (CG) limits when you load up your aeroplane with passengers, bags, and fuel. When you move your CG forward or aft and you probably know that it affects your aeroplane's performance.
There is a simple relation between your aircraft's performance and CG location: you change the amount of tail downforce by moving your CG forward and aft and lift you need for stable flight. On its CG your aeroplane balances and that location is where the downward force acts on your aircraft. From your wing Lift acts upward at a point called the centre of lift. The centre of lift is always aft of your CG.
By creating its own force, called tail-down force, your elevator (or stabilator) balances out the moment.
Essentially, the Downward lift can be generated your tail is an 'upside down' wing. To maintain the amount of lift it needs depends on two factors: CG location, and aircraft weight.
Into the baggage compartment before you go throwing everything possible, think about this: in most light aircraft while having an aft CG definitely improves performance. The difference will only be a few extra feet-per-minute of climb rate and a few extra knots of airspeed.
On your next long cross country, an aft CG might help you get to your destination a few minutes early while it doesn't make a huge difference.