mmm hard one to tackle this really, i guess its all down to your pain threshhold and adrenalin level at the time it happens.
i play up front, i always have done and even back in splatmaster days i used to like ...no LOVE bunkering people. and increasinly it has become an even bigger part of the game.
are you bothered about any particular part of you getting shot? a lot of people seem to have this thing about getting shot in the face....if that is a problem then make sure you use a mask with a solid face rather than a flexie then if you do get a close one in the mush, you wont feel it at all!
getting over it 100% will come from experience, it will happen at one time or another and afterwards you will look back at it and realise that it want that bad, a close up shot is in actual fact still moving at more or less the same speed as a full range shot and doesnt hurt any more, i personally tend to feel them less as i am usually pumped and dont even notice it till im in the bath later that day.
one thing i do recomend tho is a box
now avoiding it is a skill in its self, both for yourself and your team. if a mugging is going to be avoided then i would guess that 90% of the time the person actually being hit can do nothing about it, but his team mates can, by not letting the other team get into that position.
if it comes down to a mug or be mugged situation, DONT think about it, if the idea comes into your head just do it! go with your gut instinct, heheh use the force a little.