I am coming soon: this is the final coming, to judge and to inaugurate the Messianic kingdom. The time of distress and suffering is followed by the second coming of Christ (see 1.7; 22.7, 12, 20).
Hold fast what you have: see the comments at 2.25.
So that no one may seize your crown: see the comments at 2.10. The crown that Christ gives to his followers as the prize for their faithfulness must be kept safe from all who would, by some means, take it from them. What is meant is that they are to remain faithful so as not to lose their ultimate reward: life with Christ in the Messianic kingdom. Other ways of expressing this clause are “so that no person may take away (or, steal) your victory prize by force” or “so that no one may be able to use force and steal your prize that shows that you have conquered.”
Quoted with permission from Bratcher, Robert G. and Hatton, Howard A. A Handbook on The Revelation to John. (UBS Handbook Series). New York: UBS, 1993. For this and other handbooks for translators see here .