Sun Square Pluto
The sun represents our vitality and our conscious ego, the self and its expression. It establishes our will to live and our creative force. It is associated with spontaneity and health. A well aspected Sun will describe a person who has heart, who cares for others both in general, and at the personal level. A poorly aspected Sun will describe a person who either has much more difficulty accessing this love and caring ability. In your chart the position of the sign represents your life purpose and style in which your make your mark in the world.
Sun Square Pluto
The energy and challenges indicated by this square can be difficult to deal with, as the unintegrated negative tendencies of Pluto can be fully present. Plutonic energy, allowing you to redirect it towards more positive channels which are associated with your solar path.
However, you will have to remain aware of how you are expressing Pluto, as its peculiar quality will still be vitalized and cannot be nullified, only used in a wiser manner. The Pluto tendencies of ambition, force, power, domination, aggression, and extremism can also stimulate similar tendencies in an assertive Sun and will exist as motivating and compulsive factors in your character.
You may experience considerable inner tension as a result of this challenging planetary relationship, often finding it difficult to 'break through barriers' which appear to prohibit the attainment of your ambitions. This is Pluto attempting to force you towards an inner transformation, the need for which you will recognize whenever the pressures of frustrated intentions increase, until you find it hard to live with and in some way 'blow up', releasing the pressure.
Compromise and co-operation are two lessons which need to be learned as soon as possible, as well as more inner moderation. Once you achieve a balance between your being receptive to others and your dominating tendencies wanting them to submit to you, then you should find that the quality of your relationships begins to improve in a creative and constructive manner.