Mercury - me too. I don't force myself to go at all, I just love it. Not so much the gym but I love the classes, esp spin, and I love pole fitness! If I didn't enjoy it I wouldn't do it so much but I am at the stage where I ab hate missing a session. I am lucky in the fact that I incorporate it into my working day. I work for a really small company so I go to the morning classes every day but take that as my lunch hour.
Yes, after a couple of rest days in a row if life´s too busy I´m getting a bit twitchy and desperate to throw some heavy things around Mmmm, endorphins
If you find it a struggle to fit it in with a long work day and commute, there are loads of bodyweight workouts you can do at home in the living room/garden. You can also gain a lot from an intense 5 min session, or a few throughout the day if that suits your lifestyle better. Maybe set yourself a challenge every week - if you´re starting out, maybe 50 squats every day, or 100 push ups etc. Easy to adjust to whatever level you´re on (just make sure it´s a bit of a struggle...).
I run 3 mornings a week and try to swim twice a week. I like to go for a bike ride (around 10 miles) at the weekend. I also walk to and from work 5 days a week which is 2-3 miles a day depending on which route I take.