25 is definitely not too old. I started a Uni degree in my mid 40's because because it took me that long to stabilise my life enough and with good Psychologist support I finally realised it is possible. My intelligence is only just average, I work full time and still struggle at times, however am doing very well. You just need to want to do it, and ask for help when things get tough, as sometimes they do. The upside is the incredible satisfaction of learning new interesting things, improved self esteem and when you do get good results, they are often a reward for your hard work.
