When you catch a cold you're body produces mucus as a defence mechanism.When you sneeze out your mucus you're also clearing your body from some germs and toxins.So the faster you clear your mucus the faster your body is free from a some amount germs and toxins and you feel better faster also.But sneezing out mucus also needs high pressure of air so the much air you can store in your lungs the much faster you can sneeze out more amount of mucus.But if your lungs don't have high capacity then it may take some time because you can't clear your mucus faster for having less lungs capacity.So don't smoke.Smoking cigarettes decreases your lungs capacity so you can't rid of your cold faster.