Make up one's mind

From Fresh Dictionary

English

Verb

make up (one's) mind

1. ((idiomatic{{#if:|, {{{2}}}{{#if:|, {{{3}}}{{#if:|, {{{4}}}{{#if:|, {{{5}}}{{#if:|, {{{6}}}{{#if:|, {{{7}}}{{#if:|, {{{8}}}{{#if:|, {{{9}}}}}}}}}}}}}}}}}}})) To decide; to reach a conclusion.

   I can't make up my mind whether to have ice cream or cake.