Key to success in building and maintaining a quality
exercise plan is to make sure that it's something that you can live with. I've found in the past that I'll get really pumped and excited about a new regimen ... only to burn out after a couple of weeks. The level of fitness that you're willing to target needs to be based on a structure that you can fit into your lifestyle. While invariably improving your health means that
some changes in lifestyle are necessary, only you can decide how much. This applies to both exercise and nutrition.
It's better to be consistent with less exercise than to ride a rollercoaster of too-much, then total-abstinence ... then back on the bandwagon (feeling bad that you "fell off" in the first place). Challenge yourself ... but don't go overboard. Small incremental improvements are usually best.