Is it bad for me to “crack” myself?

It depends.  You probably won’t do any serious harm to yourself, because your body won’t relax enough for that to happen.  But if you are “cracking” your self a lot, please know you’re only moving the joints that already move enough (and maybe even too much).  There are likely a few joints that ARE NOT moving enough, and you are not helping the situation by continually moving the ones that move enough already.  You may be causing hypermobility (moving too much) in those areas that you’re cracking.  This can predispose your spine to degeneration in the future only because there are still joints in your spine that aren’t moving well (hypomobility), which causes an imbalance of movement and work load.  Hypomobile joints aren’t getting enough joint fluid, and hypermobile joints are moving too much as they try to “pick up the slack” of the hypomobile joints, and this combined scenario may cause degeneration.