Some people are loners. They love to do everything alone, whether it's solving problems or doing sports. I'm not a loner, especially concerning sports. I have done team sports my entire life and have cherished the collective locomotive that is needed to succeed.
There is a reason why I end up training more than usual every time I go home to Norway. Either I'm training with my buddies, my family or both, I'm always outside trying to experience the nature I miss so much. But it's still really hard to get motivated to do so if I don't have anyone to share it with.
Training partners push you to perform better. Competition is one aspect of partner training that shouldn't be underappreciated. Having someone to keep up with or challenge is highly motivating and encourages both parties to put in the extra work.
But competitions isn't the only thing. I always have a bigger problem getting out to do something than to actually doing the activity. Having a commitment with someone can completely remove this obstacle and encourage to a more frequent training regime.
Many will say that finding a training partner that has the same athletic level as you would be preferable, but for many activities this isn't important at all. It's just as important to find someone you enjoy hanging out with as often as possible. Activities can almost always be individually customized anyways. In short, find a training partner and get motivated!