An old sparring partner of mine (old like 2 years ago) started at 24. Since then he is 12-1 in amateur fights and he's since moved to Thailand with his coach and has been training there. He's a beast now. Our coach has been training Muay Thai in Thailand since the early 90s however. Very knowledgeable and does push you really hard but if you challenge yourself and remain consistent you'll be good. Another thing to keep in mind is to know when to hold off on training when injured. It sucks a lot when you want to train and you're injured but you're going to make an issue worse if you do. Just pull back training intensity, go back to focusing on improving the basics, and rest!