Pain is opposite of pleasure. Pain is something not desired by a healthy mind. The craving for pain cannot be for pain but for a type of pain which in its acuteness starts producing pleasure. As Fyodor Dostoevsky wrote in his Notes from the Underground, such pleasure may arise from immensity of loathing amid most intense of pain. In psychotic situation known as masochism, a subject derives pleasure by inflicting pain upon himself.
I have a certain observation about normal pain stored in body. When I use word 'stored', it is to suggest that certain relaxation methods let this pain end and that is why it is called 'stored' unless you do something about it. The pain is often not very obvious to notice but in certain parts of your body it's stored because of your negligence. In cases of acute pain in any part of your body, you become very aware of that part of your body and time starts taking toll on you. Time becomes heavier because incessant rapid stream of thoughts triggered by the sensation of pain makes your mind stuff grow exponentially. Even in moderate cases of pain you feel certain uneasiness and you do not really become very conscious of the fact that it is because of pain that you do not feel at ease and even feel peevish at times, whereas everything seems to be at ease from the outset. As Buddha said in his Noble Truths, becoming aware of the suffering is the first step towards removing it (or at least reducing it), knowing that pain is present helps in getting rid of it. This subconscious pain in form of feelings or at the gross level of physique makes you very uneasy in your day to day business. if it is not present, very simple looking things would engross you and time would start flying with wings of happiness.
Acceptance is the alchemy that transmutes the pain into the bliss. The pain is not in itself the problem but rather the situation of which it's a part. The situation makes pain either acceptable or totally unacceptable. You know that there are certain situations when pain is considered pleasure. This goes on to prove that it's your attitude towards the pain which decides your feelings. Acceptance of pain tends you towards spiritual awakening because it makes your life a complete whole. You are quick to accept pleasure because it's like happiness, your true nature; but you shun pain and detest it. When you develop the attitude of a witness towards streams of pain and pleasure in life you don't shun pain. You transmute it into bliss by acceptance. Some pain is inevitable, suffering is optional.
image source: here and here