Motivating yourself will be a lot easier if you can find something you really enjoy doing to keep fit, rather than settling for boring exercises at home that you have no real interest in - a specific sport or something you can do with a friend/partner ... some reason that makes it less about actually exercising and more about the overall experience that goes with it.
I play badminton a lot and love it - it requires no motivation for me because I look on it as social life (team sport) and also as an art form, where no two games are ever the same (crafting new shots, analysing styles of play, tactics etc).
BUT, as age catches up with me, I have begun swimming/running at least once as week in place of a badminton session - I don't particularly enjoy either, so find it very hard to get motivated enough to do them, but I do because it is better for my overall fitness and I can do both for free, whereas playing badminton all the time gets expensive - the following are all things I look to in order to motivate me to either Swim/Run:
1. Weather - if it's Sunny, then a run is not just a run - it's a chance to get outdoors and top up my sun tan - over the Summer, I found a lovely peaceful spot where the sun would set and I could lay on a grassy bank in between running.
2. Location - I will only run in picturesque settings. Find somewhere with nice views, gardens, nice surroundings or somewhere near some other activity that you can take advantage of at the same time - for example, go to the gym when you know they'll be showing something on the sports/music channels that you know you won't be able to get on your own TV channels at home, go running past your favourite car showroom/fashion store to add interest. Go cycling and find a nice route along a river with fields full of horses either side and pub at one end.
3. Added bonuses - If I go swimming I will almost certainly have the chance to craftily check out the opposite sex...feet etc - not in an obvious, lecherous way...I mean we all find ourselves noticing people we find attractive as we go about our daily business and enjoy people watching... if, like me, you're single, then you may find yourself able to strike up conversation with a potential romantic interest... or if not, a random old character who just makes you laugh.
4. Music - I usually go swimming when there's a fitness class going on in the adjacent pool as I know they'll be some music playing, which makes it so much more enjoyable.
5. Reward - Take no shame in rewarding yourself - every time I swim 10 lengths, I'll go and sit in the Steam Room for 10 minutes. If I've been running for an hour, it's not gonna hurt if I have a single bottle of beer afterwards. If I check myself out in the mirror after a few swim sessions and tell myself I look slimmer and have a nice glow in my cheeks, then I'll feel physically better too and will be more likely to go again. Tell people you've been doing excercise - brag about how much you did, be positive, take the credit that follows!
6. Identify Ruts - is there a time in the week where you're usually bored and wonder why the hell you're watching this trashy tv show, or refreshing your facebook page for the 10th time in an hour.... if there is, tell yourself that's ridiculous and admit you're bored and do excercise instead.
All the above generally helps me to stay motivated, so hope that helps
TTG