If you want to pursue a career as a professional psychologist (which necessitates completing a very competitive to get onto graduate course i.e. the DClinPsy, DEdPsy, masters in forensic psych etc), it's probably sensible to pursue as much clinical and related work experience as you can, since you will need it I as I understand for those courses.
If you're not planning to pursue a career as a professional psychologist you absolutely will need to pursue any of the generalist internships any degree student will be applying to, to be competitive with any other grad. The days of a degree getting you a job by itself are long and truly gone - you need to be getting work experience through internships and making yourself employable otherwise.
That said most internships tend to be aimed at second year students as I understand. So it's reasonable to aim for this in second year.
It's probably also sensible to stop thinking about the summer as a "holiday" because really once you leave school that ends pretty much for the rest of your life. During uni it's a time to do internships/placements/research projects/etc (even part time casual work to save money for the following year), and once you're in a full time job as a graduate (whether a graduate role or not) you'll be working year round with the exception of your annual leave (which you may well take a good chunk of during the summer, however it won't be anywhere near "summer holiday off" like in school; a few weeks here and there, and everyone else will be aiming to take some leave in the summer as well usually).