Do you use a particular time signature to make the "beat" or do you just freestyle? The tempo of the track is like a guideline or a boundary. It lets you know when to start and stop and is basically the backbone of percussion based music. You should, at least, have a rough idea of the tempo range that you are working in before you start writing chord progressions and melodies and such.
Are you using smaples or loops? You can loop or chop a sample and it can sound great... Until you put a beat behind it. If It doesn't fit, it just doesn't fit. There are ways around that like time stretching and the like but again if you don't even know the approximate tempo of your project, then that is useless to you. Some commercially sold loops are not chopped very well so if you are using those you may need to trim them up a little to get them to loop exactly as you want them to.
My suggestion to prevent this from happening in the future is to lay down a very basic drum pattern, beforehand, or use a metronome to help you keep time.