You can sharpen the bit yourself, provided you maintain the geometry so the bit does not become unbalanced. For the most part it is easier to have a shop do it. Why it needs sharpening is difficult to answer without more information. What type of wood are you cutting and how much are you removing? What brand is the bit? Is the bit steel or carbide? Is the bit discolored?
Here are some thoughts which may help you get better results: A simple rule of thumb is to remove no more than 1/4" of material at a time. To remove more than this make multiple passes. Do not try and force the bit along. Give it time to cut. Use a slow even speed as you feed the bit along the wood. Clean off any residue from your bit. Any build up can cause the bit to stick and performance drops. Don't buy poor quality bits. When possible use a 1/2" shank bit since it will be stronger and have less vibration than a 1/4" shank bit.
Here are some thoughts which may help you get better results: A simple rule of thumb is to remove no more than 1/4" of material at a time. To remove more than this make multiple passes. Do not try and force the bit along. Give it time to cut. Use a slow even speed as you feed the bit along the wood. Clean off any residue from your bit. Any build up can cause the bit to stick and performance drops. Don't buy poor quality bits. When possible use a 1/2" shank bit since it will be stronger and have less vibration than a 1/4" shank bit.
