In the beginning, Nathan felt the burden of the Irrelevant List keenly. Nathan assumed that since Harold was not leaping into action that Nathan held this weight alone. Harold felt it too but he tried to rationalize it away as being for the greater good. Neither man shared their cargo of guilt, shame and blame. They went at it alone.
Before The Pilot, Harold carried the Irrelevant List responsibility on his own. From the taped recording of a three year old murder to the wheelchair scene- Harold was punishing himself over and over again with the knowledge and blame for the ones they did not save. This load was crushing him.
Harold hired Reese. At first Harold kept Reese at arm's length. However, to get the job done Harold had to share the knowledge of The Machine's (TM) existence with Reese. This small 'suitcase' of fault was transferred reluctantly. Yet, even such a minuscule weight makes it easier to breath and live for Harold.
Slowly, Reese and Finch started to become symbiotic. Sharing, even the little things (Eggs Benedict, Sencha Green Tea, Chess in the Park,etc) created a bridge between the two men that allowed the men to work in tandem- a yoke if you will. This yoke allowed the men to pile their respective transgressions into a cart of self recrimination that each pulled along with all their might.
Harold was able to help redistribute some of the CIA shame and culpability off of Reese. While John slowly started to relocate a lot of remorse, grief and anguish from Harold's shoulders. Some of that burden was transferred to John, others were discarded because those things never should have been assigned to Harold in the first place.
The biggest indictments for Harold were Grace, Nathan and T.M. End of Season One, Finch opened the *Grace Trunk* and took out the photo album for John to see. End of Season Two; T.M. and Nathan were shared. Reese's "You planned this" and "You lost a friend" show us that John is gladly assisting Harold in hefting these concerns.
In return, Reese volunteers, "In an airport seven years ago." Which is a relief because half way through Season Two, the Dead Reckoning arc, John was trying to bear that weight alone. However, we saw Finch not allow Reese to strap that responsibility or blame onto John's back alone. Finch was right there holding the bomb vest up along side John. This was *their* millstone not John's past coming back to haunt him as Reese tried to argue.
Later in One Percent and Booked Solid, Reese is still trying to hold a boulder of stigma on his own- refusing to share with his partner. Finch by now can see how unbalanced they are with the cart tipping dangerously to John's side. Finch keeps at him until Reese finally allows the chunk of responsibility and blame to fall to the ground and be examined. There, Finch can laugh and explain to Reese how the boulder is not his to carry and certainly not theirs.
They leave the rock of ages past by the wayside and continue on their journey. This allowed the two to act as one team when Season Two's finale kept them apart. Reese might not have been able to see Finch or know what Harold was planning, but any team of oxen who have been yoked together through rough and rocky terrain can anticipate the movements of the other. People who are inexplicably sewn together can not simply be rendered asunder so easily.
As the men traveled, the overwhelming strain of their personal encumbrances are reduced. Being able to rest, breathe and regroup has allowed Reese and Finch to take stock. They can now see the situation for what it is because the light is no longer being blocked by the pile of accountability they heaped onto themselves. They are no longer kept in the shadow of their sorrow and duty. Each man still has baggage that they refuse to share but the majority of the load has been placed between them. A burden shared is now a burden halved.