I have the same problem! But I've taken to forcing myself. If I can just get myself out the front door, it's easy to hop on my bike and go. So I force myself out the front door as soon as I think of it, whether it's raining or dark out or a hot, hot day.

Keeping things right there and ready are a big help. I fill my water bottles back up as soon as I come in, kick off my biking shoes at the door, and have a shelf full of cycling gear (plus poncho) with a laundry basket for shucking off day-wear into just beside them. Having everything right there and keeping my bike within sight + easy access of the front door is really motivating because it's just so easy. No hassle. No reason not to.

But it's also easy to make excuse after excuse after excuse not to do it anyway (oh, my bum hurts today... oh, I'm just so tired... oh, it's going to rain)... so I think to myself, "Would I rather spend an hour or two enjoying myself on a nice bike ride losing/maintaining weight, or spending twenty-four hours feeling miserable and flabby?"