The best way is to start doing your work the moment you enter office premises. This will not allow your mind to deviate from your main tasks.Once, you finished all your priority based tasks, you may allow distracted activities to enter in between your other works. The important question is 'out of 8 normal working hours' how many hours or minutes your mind is taking the deviation and to determine it - you need to make constant notes daily. The more the time going in distraction the more the need for you to avoid distraction and the less the time in distraction the lesser efforts you need to cut that distractions. Sometimes, distractions infact - enhances your work performance...a sweet call from sobody you love...a good news, a healthy discussion....etc, etc acts as tonics of energy at work. finally, don't say goodbye to distractions but take effective steps to curb those unnecessaries.