Every journey begins with a single step. I used to chant this mantra to myself while I walked up stadium steps. Eventually I made it to 18,200 ft. Mt. Kala Patar in Nepal and gazed on Mt. Everest. One day I stood at the Mexican border with 2663 miles of trail between me and Canada. The first step was kinda weird and the last thing I could think about was Canada so I thought about where the next source of water might be.
If I had given too much thought to end goals, I probably would have paralyzed myself with inaction. I had big goals, obviously, but had to start at the beginning. Always give yourself permission to start at the beginning. This has been the hardest lesson in life for me to learn.
Female, 5'3", 49, Starting weight: 163lbs. Current weight: 135 (more or less).
Starting squat: 45lbs. Current squat: 180 x 2. Current Deadlift: 230 x 2
I didn't know how to do it so I just followed what ever routine I could figure out what to do. If I had it to do all over again, I would have done something more simple right from the start.
In my later teens I had a good mentor that taught me how to do it right. I was taught to train every muscle in the body to make it proportional, and that meant I HAD to squat. And like I said, if I could have done anything all over again, I would have made my workouts more simple. More time on 3-4 main lifts done heavy and hard and less time on lighter useless exercises. I might have even done floor presses instead of bench presses because with that you don't need a spotter.
And I think that should be good motivation in of itself, to know you are doing it right. All the other kids are doing only benching and curls, won't get the results, and will end up quitting and turning into mush as they proceed out of high school and into their later years in life. Then they'll have to tell others stories about how they used to bench 300 lbs even though it never really happened.
You get what I'm saying? Do it right and you will get the results!!! You will get stronger than the others. It takes time though, it doesn't happen over night. A log book can be helpful, but it always worked for me just to take a mental note instead. You won't be strong right away, you can't. But you can get stronger next week than you were this week. You can lift 5 more lbs. And if you do that over the years, it adds up. When you get older people will look at you and think you are naturally gifted, but they won't realize the hard work you put into it, that you had to do it to get that way.
Also, maybe you just don't want to spend your life in the gym. Maybe you want to play instead and chase girls. That's fine. 2 workouts per week is plenty. That's what Arthur Saxon used to recommend and he was the strongest man in the world about a century ago. Less workouts are better for the lazy because they keep you consistent, there's never an excuse to miss a workout. For example, if you plan on lifting on Monday and Thursday, you can always switch the workouts if you end up with something to do that day, no big deal. You can push a workout back or forward a day.
I hope that helps. Like I said, if you REALLY want it you'll do it. And also, KNOWING that you'll get the results will be a motivator. Every workout should see a benefit. Simple workouts work just fine, better than complicated ones. Keep it simple and progressive and you will see the results. If you really want it bad enough, that should be enough to motivate you.
Read the book "Dinosaur Training" by Brooks Kubik. If that doesn't motivate you, nothing will.
I did several false starts, where I ended up quitting. For me what got me to keep on was to find a program where I could see a steady progression (Starting Strength, it was) and doing it with a friend at first. At first I needed him to go with me to bother, but eventually I started looking forward to it. Now our schedules don't match often, but we still try to workout together when we can. If he's not able to train, I'll go by myself.
Write down what you lift, that's good advice as well, so you KNOW what you lifted last time, and can improve.