A workout partner can give you a lift

Oftentimes, I get drowsy. . .very, very, drowsy. During these times of profound laziness and minimal productivity, I lose motivation to climb out of bed, let alone get dressed and jog three blocks to wherever my workout would be. I'd be lying if I said I never convinced myself five more minutes turned five more hours of sleep was the way to go. I'd also be lying if I said I never made it to the gym with one bloodshot eye, did some stretches and walked back home having accomplished nothing. Sometimes, you just don't feel up to it.
Luckily, there exists a rotational system of laziness and on days you feel glued to the couch, there will be someone to pull you up. Such a person is there not to make you feel better about yourself but to make you be better. With the potential to be your mentor, spotter, coach and friend, a workout buddy is a valuable asset to have.
Besides making an otherwise monotonous and tedious routine more enjoyable, the logistics of having a partner are undeniable.

Accountability
There's no denying this concept anymore: it's much easier to let yourself down than someone else. While it's so easy to find justifiable excuses not to exercise, they are, in the end, still excuses. Letting yourself off the hook seems to bear no immediate consequences but abandoning your partner bears the risk of wasting his/her time, appearing irresponsible, undependable and to a degree, disloyal. Even a friend has a limited amount of patience for someone who always bails on the same thing time after time. In one sense, you are guilt-tripped into doing something that's good for you all the while building time-management skills.

Male/Female Partner
On face value, pairing up with someone of the opposite gender seems counterproductive. How could you both engage in the same exercises while on different skill levels? You don't. Albeit being slightly superficial, one unsaid reason why members of the opposite gender make excellent training partners is that showing off is a good motivator for using heavier weights and with higher intensity. I believe that an alpha-male instinct kicks in and the distaste for being shown up.

Over-partnering
As great as it is to have camaraderie in the gym, going in groups can impact your results negatively if you're not part of a regimented team. Waiting for more people to finish during a rotation lessens the intensity, lowers the number of repetitions and dilutes the good burn you might feel with a steady circuit of exercises. A larger group also runs the risk of distractions and a collaborative effort by the group can convince most individuals to finish early, train easy or go out to eat. On the other hand, don't be the person who socializes - you will neither help your friends nor yourself.
Remember, you're trying to get into the best shape of your life; you face a challenge during every exercise and need to divert your full attention to beating that challenge. Keep a straight face and save the laughs for later. You won't be judged for lack of warmth, you'll gain respect.
Goals and Solidarity
Pairing up with the right person can be very difficult. Similar strengths, goals, attitudes and schedules need to fall into place in order to form a basis for consistent success. If one person is a significantly fit, he or she will under-challenge himself, over-challenge their partner or waste time changing the equipment to the fit needs of both members. A balanced individual can keep rest intervals in check, talk you out of quitting, inflate your expectations of yourself and push you towards the person you want to be.
If one person wants to maintain or lose weight while the other is looking to put on 30lbs, choosing one routine may end up counterproductive to at least one party. Similarly, if the partners don't share a common goal, the imbalance of benchmarks can throw both off. However, if you do choose someone who is knowledgeable, reliable, motivated and a good fit, you will immediately feel the positive energy as well as a renewed fondness for weighted ab crunches. . .
But more importantly, there is something different about the bond created between two individuals experiencing the same struggle that outlasts the gym. Your partner is a mirror reflecting how much effort you're putting in. Our natural distaste for losing in front of others and egos force our efforts beyond our comfort zone and into the realm of failure. Switch the scenario around: we need to make sure our partner doesn't fail, yet we also want to gain the competitive advantage in the pair, and this is achieved through trying harder each time.