There are many different aspects to consider.
I cannot recall whether you said anything about children, or a future wish to have any. Term-time, I see mine 2 hours a day. I'm lucky to have found great childcare available from 7am, which allows me to start work by 7.40am most days and it is the absolute latest I'd be in work for without feeling too rushed off my feet. With meetings etc. you need to plan to be in work for at least an hour before school starts to get prepared for the day.
You mention pay. If you are considering teaching Maths (as a shortage subject) there are routes into teaching that will pay you a tax-free bursary in addition to your student fees. You could end up earning more during your training than the people who train you with many years experience, BUT you will alsohave to cope with a sudden £10k pay drop when you qualify.
Can you deal with being stuck at around £25k for many years? Performance-based pay is, in many schools, a thin veil over the fact that schools are severely out of money and will do whatever they can to keep you on as low a salary as possible. So even great performance from yourself all year may mean that due to circumstances beyond your control your classes do not achieve the arbitrary number grade you need. I'm recognised to be excellent at my job, but have been stuck at my current pay grade for 6 years; my similarly-qualified DH even for longer. It's soul-destroying seeing the effort you put in and how little it is valued.
You mention time. I've done this job for 15 years. I refuse to work much more than 2 hours extra a day, bringing my average working hours to about 50 a week. But I can make up a lesson on the spot, improvise and work throgh my breaks and lunches as well as using every time-saving method in the book. I'm still constantly exhausted, because teaching means full-on performance for about 6-7 hours a day. You will always be in contact with pupils; it is very rare to get a proper break, even if you don't follow my system - too many emails to repond to, phone calls to make, requests from students to talk to you, mini-meetings, paperwork etc.
Can you deal with, effectively, having to "behave" every time you step out of your front door? I've met students on holiday while trying to sunbathe, been seen shopping for personal hygiene items, been sworn at by a group of particularly lovely students on public transport in the presence of my own children etc. You can, and will, be searched for and found on social media and have kids and parents watch your every move when out and about. Even when, like me, you live a good drive away from work.
Can you deal with the emotional side of teaching? Behaviour has deteriorated massively since I first started teaching; both myself and colleagues have been assaulted by students often bigger and strnger than ourselves and still having to face them daily afterwards. Being sworn at is so common now most members of staff don't have more than a detention to be able to deal with this (often, there is a two-tier system, but that is a different matter). Even more common is disruption to your lesson - deliberate, through obvious disinterest (Catherine Tate used to make fun of it in her role as Lauren, but the portrayal is fairly accurate for many older students I have taught) or accidental, through people walking in and out of your classroom to pass on messages, pulling out students, events happening etc.
Can you deal with the stresses of observations? Having 1-2 people who often know nothing about your subject judge you on a mere hour or half an hour two to three times a year and through this system evaluate your worth to the school? Which means that if little Johnny decides to swear at Jane (his GF he has just broken up with) and then Nancy and Dave get involved with their mates and Wayne is refiusing to do anything, because he already has been given 3 detentions before arriving to your lesson and is pissed off at his dad, all this may turn into your lack of control over the class, wreck the carefully-planned lesson and allow people who know next to nothing about the class or the subject tell you you're not good enough.
Can you deal with constant changes made to what you teach and the way you teach? People will tell you that planning a lesson gets easier over time (it does) but that doesn't mean much less work when you have to re-upload everything into a new common format for the department, deal with almost annual changes to the curriculum and accommodate whatever the newest fad is into your lessons.
How good are you at saying no? To parents who request practically 1:1 tuition (extra work, catch-up during lesson etc.), senior leaders guilt-tripping you into giving up lunchtimes, afternoons or holiday days (i.e. family time, see first point) to do extra revision classes or lead enrichment, being asked to give up yet another prep lesson to do emergency cover? Being told to fill in pointless paperwork, often duplicated? Being told at almost no notice that there will be an extra meeting after school, even if you need to pick your kids up from childcare? You can say no to most things, but it takes a lot of balls to constantly stand up for your right to refuse and may make you a target to be moved on.
How good are you at prioritising? The job will never be done, no matter how many hours you work. Everything is a priority to different people in your school and most of all to the 150-450 students you will be dealing with, depending on your subject.
How good are you at dealing with frustrations? "computer says no" is fairly common, expecially when something you think may be a good idea involves money and endless paperwork. It is similarly frustrating when your job depends on others doing their work and seeing the tiny amount of influence you have on this (e.g. when you are held reponsible for your form's uniform standards, but Caitlin turns up in a mini skirt and with false nails every lesson and mum says the new iPhone she bought her daughter means that she now cannot afford a new skirt or varnish remover for the next four months).
By the time I get out I will have done the job for 20 years. I'll have been disillusioned for about half of that time. My students generally like me and recognise I'm doing a good job. But even though I've learned to say "no" quite firmly to many requests to preserve my own health and sanity (therefore work less, but also do a less good job than I could do if I still saw the point in it), I'm exhausted. The job never stops, especially in your head. No two days are ever the same, but year on year the issues you face don't change. I've lasted this long out of sheer determination and with the knowledge that (as a shortage subject teacher who is bloody good at what I'm doing) I will always find another job should I become uncomfortable in the eyes of senior staff (who are younger and less experienced than me). Everyone I've trained with has already quit. Most of my colleagues want to quit and are often only holding on because of the initial pay dop they'd face or for lack of ideas of what else to do with their lives when lack of time prevents them from exploring hobbies or realistically considering re-training.
I am passionate about education. But education is different from the reality of teaching.