Don't let your workout work you over.
You've made it to the gym and really, that's the hardest part.
But now that you're here there are some things that can easily be avoided in order to utilize your hour (yup it shouldn't have to take more than an hour) most effectively.
1) Not knowing how long you've been resting for.
That hour of training is only going to happen effectively if you time your rest between sets.
Stick to 30-60secs between sets (30 for more of a cardio fat/loss session or closer to 60 when working on size. Letting a text conversion take over during rest will only add to your time in the gym and get your head out of the game.
2) Not having a game plan.
Be clear about what body parts you're training before stepping on the gym floor.
This should be an area or group that works together to either push, pull, squat or lift. Like chest and triceps, both work to push away from your body. So focus the whole hour on things that accomplish that. You can have specific movements mapped out which is even better but don't be married to those exact ones. If there's a line for the barbell bench press, move on and find a similar way to work the same group; like a dumbbell bench press.
If you skip around from body part to alternate part it's a good chance that you're not going to fatigue one area well enough to do much good.
3) Thinking to small.
If your goal is weight loss than sitting at bicep curl machines and leg extension machines isn't the best use of your time. Think bigger!
Spend the bulk of your time on big compound (at least two joints working at same time) movements. This recruits the most muscles which burns the most calories. You'll know right away because it will be more taxing and you should feel an increase in heart rate.
Combine this with point #1 in this article and you'll have a training session worth posting to Facebook about.
4) Have realistic working goals.
If you're trying to put on muscle because you feel too skinny, 45 min of cardio probably isn't what you want to start your workouts with. You need resistance training, an excess of around 500 calories above your baseline, and about a gram of protein per pound of body weight if not more
Saying you want a bigger chest and flatter stomach is fair.
But to gain muscle the body needs extra calories, to loose weight the body needs to be in a deficit.
Doing both at the same is pretty difficult unless you're just starting out.
In which case gains come about quickly even with restricted calories. So pick what's most important, size or lean-ness, train and eat for that goal. Once you get the size for example, than you can work on knocking off some chub.
5) Thinking three weeks will negate three years of neglect.
It didn't happen overnight that you fell out of shape. It was a series of choices that became habit. You have to create a new habit of fitness and this takes time.
Give yourself three months of adherence to a plan before critiquing your body or jumping ship for a new program. And if you only stick your plan some of the time, you can't expect more than just some results.
Don't get discouraged so early in the game that you give up and go back to the way living that doesn't serve the way you want to feel about yourself.
Small consistent changes in yourself are the gold standard!
If you need help with workouts or meal plans ask for help! I'm here at writegf@gmail if you want to reach out.
You're worth the effort, stay motivated!