From fairest creatures we desire increase,
That thereby beauty's rose might never die,
But as the riper should by time decease,
His tender heir might bear his memory:
But thou contracted to thine own bright eyes,
Feed'st thy light's flame with self-substantial fuel,
Making a famine where abundance lies,
Thy self thy foe, to thy sweet self too cruel:
‘Contracted’ suggests a legal obligation, imagery which is found elsewhere in the Sonnets, for example   Sonnet 4 ,  but also means “reduced [to]” and “ shrunken .” The youth is bound and restricted to regarding his own face, just like  Ovid’s Narcissus , staring at his own reflection: 
 I am burning with love for myself. 
 This idea appears again in  Sonnet 4  when Shakespeare writes “why dost thou spend upon thyself thy beauty’s legacy?” 
 Like Ovid, Shakespeare uses the metaphor of burning in relation to infatuation with the self; here, the flame continues to be fed with “fuel”  which is self-generated  (“self-substantial”) , rather than made with another (as in marriage). 
 The  alliterative  “f"s in lines six and seven enhance the sense of the speaker’s emotion and suggests, perhaps, annoyance. 
 
 Waterhouse’s  Echo and Narcissus.
Sonnet 1