Teamwork.
If you have an automatic weapon and plenty of ammo to spare, provide cover fire while your team moves ahead. This is done by pretty much spraying in the enemy's general direction. They'll typically be in a state of being spooked and will remain hiding.
If you don't have an automatic weapon, only move when your team is shooting. Only peek when the enemy team isn't shooting.
Also, certain masks can be a bit uncomfortable to breathe in. If you do have one like this, angle your breathing downwards.
Last but not least, clothing choices.
You can either...
A. Be a bitch. Wear a sweater. Be sluggish, tired, and sweaty.
B. Don't be a bitch. Go in a t-shirt, be a speedy ninja, and realize they don't actually hurt that much.