Of course. Just try to be as determined as you can It's never too late to start something and get good at it.
Yes, absolutely. I'm 40 now, was 38 when I started. Due to a range of permanent injuries there's a LOT of things I can't do (For example: Kick above waist high!). The instructors quickly realised there was no point grading me against the syllabus, as I would do this for ten years and remain a Yellow Belt. So instead they grade me according to the syllabus IN CONSIDERATION OF what I'm physically capable of doing. I'm certainly capable of putting it into practice - so (if you're like me), you won't achieve technical proficiency, but you will become capable of defending yourself and your loved ones.
Certainly. My father started karate in his mid to late 50's (we train at the same dojo) and he's pretty good at kumite/sparring. The only issue is there are some techniques he cannot easily anymore, particularly head kicks, so he rarely uses them in sparring. If you have difficulty doing a technique due to an injury, physical constraint or immense pain, then leave it be as I think any instructor would understand. For my father, the sensei doesn't bother testing his high kicks as he knows they'll be ugly so he modifies the testing syllabus. During the warm-up, if you need a few more seconds to do a certain stretch, then take that time. Since the dojo offers 4.5 hours per week, you should view that amount of time as the bare minimum. Outside the dojo, train whenever you can as it will improve your overall performance. Don't try to zoom ahead from what is being taught, just practice what is being taught and always review from the beginning. For example, if you know 5 katas and the 5th will be on the test, practice all 5 katas, not just the 5th. For your warm-ups outside of the dojo, stretch for as long as you need.
Completely agree with Boom Headshot. Also, make the hours you put in count. In my dojo there are a lot of lazy students - every kick, punch etc is done in the laziest possible fashion. Obviously, don't do that - make every technique better than the last, and get everything you can out of every session.
Yes you sure can start martial arts at 39.I started when i was just shy of 47.I do have my limitations as far as speed and flexibility but i rely on brains instead of brawn.You have to know what you will be capable of and if you are allowed,modify your training to suit.The major problem i have is all those little niggly little injuries and pains that come with age do hinder me at times as they can take a lot longer to heal. Can you get good at it,yes of course you can.
well if this hasnt been said ill say it first no matter what you decide make sure it makes you happy, If you start training dont forget to have a good time its not worth doing if you dont/wont enjoy it and Good luck if you decide that MA is for you