Sore muscles which contain trigger points, will be painful when pressed upon. However there are many different types of pain, but confusingly only one word to describe all these sensations.
The pain from a trigger point being pressed slowly is a pain with which the person is able to relax in to, a ‘pleasant’ pain, with a beneficial outcome. This is a very different sensation to a destructive kind of pain, which we instinctively avoid for good reason.
Some pain can be eliminated very quickly. However a long-established chronic pain problem can take several goes to clear up, if the trigger points have been in place in the muscle for a long time. When this happens, pathways get formed in the nervous system, which tend to reinforce and perpetuate them. This then takes a little more persuasion to eliminate them.
A good deep tissue massage should leave you with a better range of movement and more pain free than when you arrived.