When you're a student, science is a particularly difficult subject as it involves an enormous amount of material and has a high mathematics content. If you struggle with maths you may well struggle with science.
As a student science was one of my favourite subjects. Fortunately I had an interest in science from a very early age. For some of the other students science was a nightmare which they were neither interested in or any good at (the two seem to go hand in hand!). Our science teacher was a very uninspiring individual which didn't help the class morale much at all.
To get the most out of being a student of science you need to find ways to apply what you are learning to your day to day life. Luckily with basic science this is quite easy - building water rockets, star gazing, model volcanoes etc etc. As long as science is fun your interest and motivation will be high. I remember one lesson in particular where we went out to a field and burst a balloon at one end and timed how long the sound took to travel to the other end - that was really simple but amazing as well!